U.S. patent application number 17/146881 was filed with the patent office on 2021-07-22 for reduced coating diameter chlorine-doped silica optical fibers with low loss and microbend sensitivity.
The applicant listed for this patent is CORNING INCORPORATED. Invention is credited to Scott Robertson Bickham, Ming-Jun Li, Snigdharaj Kumar Mishra, Pushkar Tandon, Ruchi Sarda Tandon.
Application Number | 20210223469 17/146881 |
Document ID | / |
Family ID | 1000005385122 |
Filed Date | 2021-07-22 |
United States Patent
Application |
20210223469 |
Kind Code |
A1 |
Bickham; Scott Robertson ;
et al. |
July 22, 2021 |
REDUCED COATING DIAMETER CHLORINE-DOPED SILICA OPTICAL FIBERS WITH
LOW LOSS AND MICROBEND SENSITIVITY
Abstract
The optical fiber disclosed has a glass fiber including a core
and a cladding. The core comprises silica glass doped with chlorine
and having an outer radius r.sub.1 between 3.0 microns and 10.0
microns. The cladding has an outer radius r.sub.4 not less than
50.0 microns. A primary coating surrounding the cladding has a
thickness (r.sub.5-r.sub.4) between 5.0 microns and 20.0 microns,
and an in situ modulus less than 0.30 MPa. A secondary coating
surrounding the primary coating has a thickness (r.sub.6-r.sub.5)
between 8.0 microns and 30.0 microns, a Young's modulus greater
than 1500 MPa, and a normalized puncture load greater than
3.6.times.10.sup.-3 g/micron.sup.2. The optical fiber has a
22-meter cable cutoff wavelength less than 1530 nm, an attenuation
at 1550 nm of less than 0.17 dB/km, and a bending loss at 1550 nm
of less than 3.0 dB/turn.
Inventors: |
Bickham; Scott Robertson;
(Corning, NY) ; Li; Ming-Jun; (Horseheads, NY)
; Mishra; Snigdharaj Kumar; (Wilmington, NC) ;
Tandon; Pushkar; (Painted Post, NY) ; Tandon; Ruchi
Sarda; (Painted Post, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING INCORPORATED |
Corning |
NY |
US |
|
|
Family ID: |
1000005385122 |
Appl. No.: |
17/146881 |
Filed: |
January 12, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62962600 |
Jan 17, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 133/14 20130101;
G02B 6/02395 20130101; C09D 175/04 20130101; G02B 6/0281 20130101;
G02B 6/03627 20130101; G02B 6/0365 20130101; C09D 4/00
20130101 |
International
Class: |
G02B 6/02 20060101
G02B006/02; G02B 6/028 20060101 G02B006/028; G02B 6/036 20060101
G02B006/036; C09D 4/00 20060101 C09D004/00; C09D 175/04 20060101
C09D175/04; C09D 133/14 20060101 C09D133/14 |
Claims
1. An optical fiber comprising: a glass fiber, the glass fiber
including a core region and a cladding region surrounding and
directly adjacent to the core region, the core region comprising
silica glass doped with chlorine and having an outer radius r.sub.1
in a range from 3.0 microns to 10.0 microns, the cladding region
having an outer radius r.sub.4 greater than or equal to 50.0
microns; a primary coating with an outer radius r.sub.5 surrounding
and directly adjacent to the cladding region, the primary coating
having a thickness (r.sub.5-r.sub.4) in a range from 5.0 microns to
25.0 microns and an in situ modulus less than 0.30 MPa; and a
secondary coating with an outer radius r.sub.6 less than or equal
to 110 microns surrounding and directly adjacent to the primary
coating, the secondary coating having a thickness (r.sub.6-r.sub.5)
in a range from 8.0 microns to 30.0 microns, a Young's modulus
greater than 1500 MPa, and a normalized puncture load greater than
3.6.times.10.sup.-3 g/micron.sup.2; wherein the optical fiber has a
22-meter cable cutoff wavelength less than 1530 nm, an attenuation
at 1550 nm of less than 0.17 dB/km, and a bending loss at 1550 nm,
determined from a mandrel wrap test using a mandrel with a diameter
of 20 mm, of less than 3.0 dB/turn.
2. The optical fiber of claim 1, wherein: the core region has a
step index relative refractive index profile with a relative
refractive index .DELTA..sub.1 in a range from 0.08% to 0.30%.
3. The optical fiber of claim 1, wherein: the core region has a
graded index relative refractive index profile with a maximum
relative refractive index .DELTA..sub.1max in a range from 0.08% to
0.50%.
4. The optical fiber of claim 1, wherein the chlorine has a
concentration in a range from 1.5 wt % to 7.0 wt %.
5. The optical fiber of claim 1, wherein the cladding region
comprises: an inner cladding region surrounding and directly
adjacent to the core region, the inner cladding region having an
outer radius r.sub.2 and a thickness (r.sub.2-r.sub.1) in a range
from 1 micron to 7 microns; and an outer cladding region
surrounding and directly adjacent to the inner cladding region, the
outer cladding region having an outer radius r.sub.4 in a range
from 50 microns to 70 microns; wherein a relative refractive index
.DELTA..sub.2 of the inner cladding region is less than a relative
refractive index .DELTA..sub.4 of the outer cladding region.
6. The optical fiber of claim 5, wherein: the relative refractive
index .DELTA..sub.2 is substantially zero; and the relative
refractive index .DELTA..sub.4 is in a range from 0.05% to
0.30%.
7. The optical fiber of claim 5, wherein: the relative refractive
index .DELTA..sub.2 is in a range from -0.25% to 0.0%; and the
relative refractive index .DELTA..sub.4 is substantially zero.
8. The optical fiber of claim 5, wherein: the relative refractive
index .DELTA..sub.2 is in a range from -0.25% to -0.0%; and the
relative refractive index .DELTA..sub.4 is in a range from 0.05% to
0.30%.
9. The optical fiber of claim 1, wherein the cladding comprises: an
inner cladding region surrounding and directly adjacent to the
core, the inner cladding region having a thickness
(r.sub.2-r.sub.1) in a range from 1 micron to 7 microns; and a
depressed index cladding region surrounding and directly adjacent
to the inner cladding region, the depressed index cladding region
having an outer radius r.sub.3 in a range from 15 microns to 40
microns; an outer cladding region surrounding and directly adjacent
to the depressed index cladding region, the outer cladding region
having an outer radius r.sub.4 in a range from 50 microns to 70
microns; wherein a relative refractive index .DELTA..sub.3 of the
depressed index cladding region is less than a relative refractive
index .DELTA..sub.2 of the inner cladding region and a relative
refractive index .DELTA..sub.4 of the outer cladding region.
10. The optical fiber of claim 9, wherein the relative refractive
index .DELTA..sub.3 is in a range from -0.25% to 0.0%.
11. The optical fiber of claim 9, wherein the relative refractive
index .DELTA..sub.2 region is less than the relative refractive
index .DELTA..sub.4.
12. The optical fiber of claim 1, wherein: the in situ modulus of
the primary coating is less than or equal to 0.30 MPa; the Young's
modulus of the secondary coating is larger than or equal to 1600
MPa; a diameter 2r.sub.5 of the primary coating is less than or
equal to 190 microns; and a diameter 2r.sub.6 of the secondary
coating is less than or equal to 230 microns.
13. The optical fiber of claim 12, wherein the diameter 2r.sub.5 of
the primary coating is less than or equal to 155 microns.
14. The optical fiber of claim 12, wherein the thickness
(r.sub.5-r.sub.4) is in a range from 10.0 microns to 17.0
microns.
15. The optical fiber of claim 12, wherein the diameter 2r.sub.6 of
the secondary coating is less than or equal to 190 microns.
16. The optical fiber of claim 12, wherein the thickness
(r.sub.6-r.sub.5) is in a range from 8.0 microns to 20.0
microns.
17. The optical fiber of claim 1, wherein the secondary coating has
a normalized puncture load greater than 4.4.times.10.sup.-3
g/micron.sup.2.
18. The optical fiber of claim 1, wherein the primary coating is a
cured product of a coating composition comprising: a
radiation-curable monomer; an adhesion promoter, the adhesion
promoter comprising an alkoxysilane compound or a
mercapto-functional silane compound; and an oligomer, the oligomer
comprising: a polyether urethane acrylate compound having the
molecular formula: ##STR00012## wherein R.sub.1, R.sub.2 and
R.sub.3 are independently selected from linear alkylene groups,
branched alkylene groups, or cyclic alkylene groups; y is 1, 2, 3,
or 4, and x is between 40 and 100; and a di-adduct compound having
the molecular formula: ##STR00013## wherein the di-adduct compound
is present in an amount of at least 1.0 wt % in the oligomer.
19. The optical fiber of claim 18, wherein the oligomer is the
cured product of a reaction between: a diisocyanate compound; a
hydroxy (meth)acrylate compound; and a polyol compound, said polyol
compound having unsaturation less than 0.1 meq/g; wherein said
diisocyanate compound, said hydroxy (meth)acrylate compound and
said polyol compound are reacted in molar ratios n:m:p,
respectively, wherein n is in the range from 3.0 to 5.0, m is
within .+-.15% of 2n-4, and p is 2.
20. The optical fiber of claim 1, wherein the secondary coating is
the cured product of a composition comprising: a first monomer, the
first monomer comprising a first bisphenol A diacrylate
compound.
21. The optical fiber of claim 20, wherein the coating composition
further comprises a second monomer, the second monomer comprising a
second bisphenol A diacrylate compound.
22. The optical fiber of claim 1, wherein the secondary coating is
the cured product of a composition comprising: an alkoxylated
bisphenol-A diacrylate monomer in an amount greater than 55 wt %,
the alkoxylated bisphenol-A diacrylate monomer having a degree of
alkoxylation in the range from 2 to 16; and a triacrylate monomer
in an amount in the range from 2.0 wt % to 25 wt %, the triacrylate
monomer comprising an alkoxylated trimethylolpropane triacrylate
monomer having a degree of alkoxylation in the range from 2 to 16
or a tris[(acryloyloxy)alkyl] isocyanurate monomer.
Description
[0001] This application claims priority under 35 USC .sctn. 119(e)
from U.S. Provisional Patent Application Ser. No. 62/962,600 filed
on Jan. 17, 2020 which is incorporated by reference herein in its
entirety.
BACKGROUND
Field
[0002] The present disclosure relates to optical fibers and in
particular relates to reduced coating diameter chlorine-doped
silica optical fibers with low loss and low microbending
sensitivity.
Background
[0003] There is an increasing demand for optical fiber transmission
capacity driven by the rapid growth of internet traffic. To
increase the transmission capacity, wavelength division
multiplexing and spatial division multiplexing have been used to
increase the number of transmission channels and advanced
modulation formats have been developed to increase the data rate
per channel. However, the number of channels and the channel data
rate are nearly at the practical limits and increasing the number
of fibers is unavoidable. Therefore, coated optical fibers with
reduced diameter are attractive for reducing the size of the
cables, for reducing fiber/cable cost, and for efficient use of
existing duct infrastructure. It is also attractive to have optical
fibers that have low intrinsic loss and low microbending loss.
BRIEF SUMMARY
[0004] The present disclosure is directed to optical fiber cables
having high transmission capacity, low transmission loss, and
similar or smaller size compared to traditional cables or cables
with higher fiber densities. Another aspect of the present
disclosure is directed to optical fibers in the cables having small
diameter, low transmission loss, low microbending loss, and high
puncture resistance.
[0005] One aspect of the present disclosure provides an optical
fiber, comprising: a glass fiber, the glass fiber including a core
region and a cladding region surrounding and directly adjacent to
the core region, the core region comprising silica glass doped with
chlorine and having an outer radius r.sub.1 in a range from 3.0
microns to 10.0 microns, the cladding region having an outer radius
r.sub.4 greater than or equal to 50.0 microns; a primary coating
with an outer radius r.sub.5 surrounding and directly adjacent to
the cladding region, the primary coating having a thickness
(r.sub.5-r.sub.4) in a range from 5.0 microns to 25.0 microns and
an in situ modulus less than 0.30 MPa; and a secondary coating with
an outer radius r.sub.6 less than or equal to 110 microns
surrounding and directly adjacent to the primary coating, the
secondary coating having a thickness (r.sub.6-r.sub.5) in a range
from 8.0 microns to 30.0 microns, a Young's modulus greater than
1500 MPa, and a normalized puncture load greater than
3.6.times.10.sup.-3 g/micron.sup.2; wherein the optical fiber has a
22-meter cable cutoff wavelength less than 1530 nm, an attenuation
at 1550 nm of less than 0.17 dB/km, and a bending loss at 1550 nm,
determined from a mandrel wrap test using a mandrel with a diameter
of 20 mm, of less than 3.0 dB/turn.
[0006] In some embodiments, the core region has a step index
relative refractive index profile with a relative refractive index
.DELTA..sub.1 in a range from 0.08% to 0.50%.
[0007] In some embodiments, the core region has a graded index
relative refractive index profile with a maximum relative
refractive index .DELTA..sub.1max in a range from 0.08% to
0.30%.
[0008] In some embodiments, the grade index relative refractive
index profile is an .alpha.-profile with a value of .alpha. less
than 10.
[0009] In some embodiments, the chlorine has a concentration in a
range from 1.5 wt % to 7.0 wt %.
[0010] In some embodiments, the cladding region comprises pure
silica or SiO.sub.2 and has a relative refractive index
.DELTA..sub.4 in a range from -0.05% to 0.05%.
[0011] In some embodiments, the cladding region comprises
down-doped silica with a relative refractive index .DELTA..sub.4 in
a range from -0.25% to 0.0%.
[0012] In some embodiments, the cladding region comprises: an inner
cladding region surrounding and directly adjacent to the core
region, the inner cladding region having an outer radius r.sub.2
and a thickness (r.sub.2-r.sub.1) in a range from 1 micron to 7
microns; and an outer cladding region surrounding and directly
adjacent to the inner cladding region, the outer cladding region
having an outer radius r.sub.4 in a range from 50 microns to 70
microns; wherein a relative refractive index .DELTA..sub.2 of the
inner cladding region is less than a relative refractive index
.DELTA..sub.4 of the outer cladding region.
[0013] In some embodiments, the relative refractive index
.DELTA..sub.2 is substantially zero; and the relative refractive
index .DELTA..sub.4 is in a range from 0.05% to 0.30%.
[0014] In some embodiments, the relative refractive index
.DELTA..sub.2 is in a range from -0.25% to 0.0%; and the relative
refractive index .DELTA..sub.4 is substantially zero.
[0015] In some embodiments, the relative refractive index
.DELTA..sub.2 is in a range from -0.25% to -0.0%; and the relative
refractive index .DELTA..sub.4 is in a range from 0.05% to
0.30%.
[0016] In some embodiments, the cladding comprises: an inner
cladding region surrounding and directly adjacent to the core, the
inner cladding region having a thickness (r.sub.2-r.sub.1) in a
range from 1 micron to 7 microns; and a depressed index cladding
region surrounding and directly adjacent to the inner cladding
region, the depressed index cladding region having an outer radius
r.sub.3 in a range from 15 microns to 40 microns; an outer cladding
region surrounding and directly adjacent to the depressed index
cladding region, the outer cladding region having an outer radius
r.sub.4 in a range from 50 microns to 70 microns; wherein a
relative refractive index .DELTA..sub.3 of the depressed index
cladding region is less than a relative refractive index
.DELTA..sub.2 of the inner cladding region and a relative
refractive index .DELTA..sub.4 of the outer cladding region.
[0017] In some embodiments, the relative refractive index
.DELTA..sub.3 is in a range from -0.25% to 0.0%.
[0018] In some embodiments, the relative refractive index
.DELTA..sub.2 region is less than the relative refractive index
.DELTA..sub.4.
[0019] In some embodiments, the outer radius r.sub.4 is less than
or equal to 125 microns; and the thickness (r.sub.6-r.sub.5) is
greater than 10 microns.
[0020] In some embodiments, the in situ modulus of the primary
coating is less than or equal to 0.30 MPa; the Young's modulus of
the secondary coating is larger than or equal to 1600 MPa; a
diameter 2r.sub.5 of the primary coating is less than or equal to
190 microns; and a diameter 2r.sub.6 of the secondary coating is
less than or equal to 230 microns.
[0021] In some embodiments, the in situ modulus of the primary
coating is less than or equal to 0.20 MPa.
[0022] In some embodiments, the diameter 2r.sub.5 of the primary
coating is less than or equal to 170 microns.
[0023] In some embodiments, the diameter 2r.sub.5 of the primary
coating is less than or equal to 155 microns.
[0024] In some embodiments, the thickness (r.sub.5-r.sub.4) is in a
range from 10.0 microns to 17.0 microns.
[0025] In some embodiments, the diameter 2r.sub.6 of the secondary
coating is less than or equal to 210 microns.
[0026] In some embodiments, the diameter 2r.sub.6 of the secondary
coating is less than or equal to 190 microns.
[0027] In some embodiments, the diameter 2r.sub.6 of the secondary
coating is less than or equal to 170 microns.
[0028] In some embodiments, the thickness (r.sub.6-r.sub.5) is in a
range from 8.0 microns to 20.0 microns.
[0029] In some embodiments, the Young's modulus of the secondary
coating is larger than or equal to 1900 MPa.
[0030] In some embodiments, the secondary coating has a normalized
puncture load greater than 4.4.times.10.sup.-3 g/micron.sup.2.
[0031] In some embodiments, the secondary coating has a load
transfer parameter P.sub.1/P less than 0.0178.
[0032] In some embodiments, the optical fiber has an attenuation
less than or equal to 0.160 dB/km at a wavelength of 1550 nm.
[0033] In some embodiments, the primary coating is a cured product
of a coating composition comprising: a radiation-curable monomer;
an adhesion promoter, the adhesion promoter comprising an
alkoxysilane compound or a mercapto-functional silane compound; and
an oligomer, the oligomer comprising: a polyether urethane acrylate
compound having the molecular formula
##STR00001##
wherein R.sub.1, R.sub.2 and R.sub.3 are independently selected
from linear alkylene groups, branched alkylene groups, or cyclic
alkylene groups; y is 1, 2, 3, or 4; and x is between 40 and 100;
and a di-adduct compound having the molecular formula:
##STR00002##
wherein the di-adduct compound is present in an amount of at least
1.0 wt % in the oligomer.
[0034] In some embodiments, the di-adduct compound is present in an
amount of at least 3.5 wt % in the oligomer.
[0035] In some embodiments, the oligomer is the cured product of a
reaction between: a diisocyanate compound; a hydroxy (meth)acrylate
compound; and a polyol compound, said polyol compound having
unsaturation less than 0.1 meq/g; wherein said diisocyanate
compound, said hydroxy (meth)acrylate compound and said polyol
compound are reacted in molar ratios n:m:p, respectively, wherein n
is in the range from 3.0 to 5.0, m is within .+-.15% of 2n-4, and p
is 2.
[0036] In some embodiments, the secondary coating is the cured
product of a composition comprising: a first monomer, the first
monomer comprising a first bisphenol A diacrylate compound.
[0037] In some embodiments, the coating composition further
comprises a second monomer, the second monomer comprising a second
bisphenol A diacrylate compound.
[0038] In some embodiments, the first bisphenol A diacrylate
compound is an alkoxylated bisphenol A diacrylate compound and the
second bisphenol A diacrylate compound is a bisphenol A epoxy
diacrylate compound.
[0039] In some embodiments, the secondary coating is the cured
product of a composition comprising: an alkoxylated bisphenol-A
diacrylate monomer in an amount greater than 55 wt %, the
alkoxylated bisphenol-A diacrylate monomer having a degree of
alkoxylation in the range from 2 to 16; and a triacrylate monomer
in an amount in the range from 2.0 wt % to 25 wt %, the triacrylate
monomer comprising an alkoxylated trimethylolpropane triacrylate
monomer having a degree of alkoxylation in the range from 2 to 16
or a tris[(acryloyloxy)alkyl]isocyanurate monomer.
[0040] In some embodiments, the alkoxylated bisphenol-A diacrylate
monomer is present in an amount in the range from 60 wt % to 75 wt
%.
[0041] In some embodiments, the triacrylate monomer is present in
an amount in the range from 8.0 wt % to 15 wt %.
[0042] In some embodiments, the alkoxylated trimethylolpropane
triacrylate monomer has a degree of alkoxylation in the range from
2 to 8.
[0043] In some embodiments, the alkoxylated trimethylolpropane
triacrylate monomer is an ethoxylated trimethylolpropane
triacrylate monomer.
[0044] In some embodiments, the tris[(acryloyloxy)alkyl]
isocyanurate monomer is a tris(2-hydroxyethyl) isocyanurate
triacrylate monomer.
[0045] In some embodiments, the composition further comprises a
bisphenol-A epoxy diacrylate monomer in an amount in the range from
5.0 wt % to 20 wt %.
[0046] Additional features and advantages are set forth in the
Detailed Description that follows, and in part will be apparent to
those skilled in the art from the description or recognized by
practicing the embodiments as described in the written description
and claims hereof, as well as the appended drawings. It is to be
understood that both the foregoing general description and the
following Detailed Description are merely exemplary, and are
intended to provide an overview or framework to understand the
nature and character of the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The accompanying figures, which are incorporated herein,
form part of the specification and illustrate embodiments of the
present disclosure. Together with the description, the figures
further serve to explain the principles of and to enable a person
skilled in the relevant art(s) to make and use the disclosed
embodiments. These figures are intended to be illustrative, not
limiting. Although the disclosure is generally described in the
context of these embodiments, it should be understood that it is
not intended to limit the scope of the disclosure to these
particular embodiments. In the drawings, like reference numbers
indicate identical or functionally similar elements.
[0048] FIG. 1 is a side elevated view of a section of an exemplary
optical fiber, according to some embodiments.
[0049] FIG. 2 is a cross-sectional view of an exemplary optical
fiber, according to some embodiments.
[0050] FIG. 3 is a schematic view of a representative optical fiber
ribbon, according to some embodiments.
[0051] FIG. 4 is a schematic view of a representative optical fiber
cable, according to some embodiments.
[0052] FIGS. 5A through 5C are exemplary relative refractive index
profiles of an optical fiber, according to some embodiments.
[0053] FIGS. 6A through 6E are exemplary relative refractive index
profiles of an optical fiber, according to some embodiments.
[0054] FIG. 7 shows the dependence of puncture load on
cross-sectional area for three secondary coatings.
[0055] FIG. 8 is a schematic diagram of an exemplary optical fiber
drawing system illustrating fabrication of an optical fiber,
according to some embodiments.
DETAILED DESCRIPTION
[0056] Embodiments of the present disclosure are described in
detail herein with reference to embodiments thereof as illustrated
in the accompanying drawings, in which like reference numerals are
used to indicate identical or functionally similar elements.
References to "one embodiment," "an embodiment," "some
embodiments," "in certain embodiments," etc., indicate that the
embodiment described may include a particular feature, structure,
or characteristic, but every embodiment may not necessarily include
the particular feature, structure, or characteristic. Moreover,
such phrases are not necessarily referring to the same embodiment.
Further, when a particular feature, structure, or characteristic is
described in connection with an embodiment, it is submitted that it
is within the knowledge of one skilled in the art to affect such
feature, structure, or characteristic in connection with other
embodiments whether or not explicitly described.
[0057] The following examples are illustrative, but not limiting,
of the present disclosure. Other suitable modifications and
adaptations of the variety of conditions and parameters normally
encountered in the field, and which would be apparent to those
skilled in the art, are within the spirit and scope of the
disclosure.
[0058] Where a range of numerical values is recited herein,
comprising upper and lower values, unless otherwise stated in
specific circumstances, the range is intended to include the
endpoints thereof, and all integers and fractions within the range.
It is not intended that the scope of the claims be limited to the
specific values recited when defining a range. Further, when an
amount, concentration, or other value or parameter is given as a
range, one or more preferred ranges or a list of upper preferable
values and lower preferable values, this is to be understood as
specifically disclosing all ranges formed from any pair of any
upper range limit or preferred value and any lower range limit or
preferred value, regardless of whether such pairs are separately
disclosed. Finally, when the term "about" is used in describing a
value or an end-point of a range, the disclosure should be
understood to include the specific value or end-point referred to.
When a numerical value or end-point of a range does not recite
"about," the numerical value or end-point of a range is intended to
include two embodiments: one modified by "about," and one not
modified by "about."
[0059] As used herein, the term "about" means that amounts, sizes,
formulations, parameters, and other quantities and characteristics
are not and need not be exact, but may be approximate and/or larger
or smaller, as desired, reflecting tolerances, conversion factors,
rounding off, measurement error and the like, and other factors
known to those of skill in the art.
[0060] As used herein, "comprising" is an open-ended transitional
phrase. A list of elements following the transitional phrase
"comprising" is a non-exclusive list, such that elements in
addition to those specifically recited in the list may also be
present.
[0061] The term "or," as used herein, is inclusive; more
specifically, the phrase "A or B" means "A, B, or both A and B."
Exclusive "or" is designated herein by terms such as "either A or
B" and "one of A or B," for example.
[0062] The indefinite articles "a" and "an" to describe an element
or component means that one or at least one of these elements or
components is present. Although these articles are conventionally
employed to signify that the modified noun is a singular noun, as
used herein the articles "a" and "an" also include the plural,
unless otherwise stated in specific instances. Similarly, the
definite article "the," as used herein, also signifies that the
modified noun may be singular or plural, again unless otherwise
stated in specific instances.
[0063] The term "wherein" is used as an open-ended transitional
phrase, to introduce a recitation of a series of characteristics of
the structure.
[0064] Cartesian coordinates are used in some of the Figures for
the sake of reference and ease of illustration and are not intended
to be limiting as to direction or orientation. The z-direction is
taken as the axial direction of the optical fiber.
[0065] The term "fiber" as used herein is shorthand for optical
fiber.
[0066] The coordinate r is a radial coordinate, where r=0
corresponds to the centerline of the fiber. The term "radius"
refers to a value of the radial coordinate. The term "outer
radius", when used in reference to a region of a fiber, refers to
the largest radial coordinate included in the region. The term
"diameter", when used in reference to a region of a fiber, refers
to twice the outer radius of the region.
[0067] The term "core" as used herein is a core region of an
optical fiber, representing a cylinder of material, centered at
r=0, that runs along the optical fiber's length. The core is
characterized by its radius of cross-sectional area corresponding
to confinement (e.g. 90%) of optical intensity in the optical
fiber. The core is surrounded by a medium with a lower index of
refraction, typically a cladding region. Light travelling in the
core reflects from the core-cladding boundary due to total internal
reflection, as long as the angle between the light and the boundary
is greater than the critical angle. As a result, the optical fiber
transmits all rays that enter the fiber with a sufficiently small
angle relative to the optical fiber's axis.
[0068] The term "core radius" as used herein is referred to
geometric core radius which is determined from the refractive index
profile.
[0069] The symbol ".mu.m" is used as shorthand for "micron," which
is a micrometer, i.e., 1.times.10-6 meter.
[0070] The symbol "nm" is used as shorthand for "nanometer," which
is 1.times.10-9 meter.
[0071] The limits on any ranges cited herein are inclusive and thus
to lie within the range, unless otherwise specified.
[0072] The terms "comprising," and "comprises," e.g., "A comprises
B," is intended to include as a special case the concept of
"consisting," as in "A consists of B."
[0073] The phrase "bare optical fiber" or "bare fiber" as used
herein means an optical fiber directly drawn from a heated glass
source (i.e., a "preform") and prior to applying a protective
coating layer to its outer surface (e.g., prior to the bare optical
fiber being coated with a polymeric-based material).
[0074] "Refractive index" refers to the refractive index at a
wavelength of 1550 nm.
[0075] The "refractive index profile" is the relationship between
refractive index or relative refractive index and radius. For
relative refractive index profiles depicted herein as having step
boundaries between adjacent core and/or cladding regions, normal
variations in processing conditions may preclude obtaining sharp
step boundaries at the interface of adjacent regions. It is to be
understood that although boundaries of refractive index profiles
may be depicted herein as step changes in refractive index, the
boundaries in practice may be rounded or otherwise deviate from
perfect step function characteristics. It is further understood
that the value of the relative refractive index may vary with
radial position within the core region and/or any of the cladding
regions. When relative refractive index varies with radial position
in a particular region of the fiber (e.g. core region and/or any of
the cladding regions), it is expressed in terms of its actual or
approximate functional dependence, or its value at a particular
position within the region, or in terms of an average value
applicable to the region as a whole. Unless otherwise specified, if
the relative refractive index of a region (e.g. core region and/or
any of the cladding regions) is expressed as a single value or
parameter (e.g. .DELTA. or .DELTA. %) applicable to the region as a
whole, it is understood that the relative refractive index in the
region is constant, or approximately constant, and corresponds to
the single value, or that the single value or parameter represents
an average value of a non-constant relative refractive index
dependence with radial position in the region. For example, if "i"
is a region of the glass fiber, the parameter .DELTA..sub.i refers
to the average value (.DELTA..sub.ave) of relative refractive index
in the region as defined below, unless otherwise specified. Whether
by design or a consequence of normal manufacturing variability, the
dependence of relative refractive index on radial position may be
sloped, curved, or otherwise non-constant.
[0076] The average relative refractive index (.DELTA..sub.ave) of a
region of the fiber is determined from:
.DELTA. a v e = .intg. r inner r outer .DELTA. ( r ) dr ( r outer -
r inner ) ##EQU00001##
where r.sub.inner is the inner radius of the region, r.sub.outer is
the outer radius of the region, and .DELTA.(r) is the relative
refractive index of the region.
[0077] The "relative refractive index" as used herein is defined
as:
.DELTA. ( r ) % = 100 n 2 ( r ) - n SiO2 2 2 n 2 ( r )
##EQU00002##
where n(r) is the refractive index of the fiber at the radial
distance r from the fiber's centerline AC (r=0) at a wavelength of
1550 nm, unless otherwise specified, and n.sub.SiO2 is the index of
the outer cladding at a wavelength of 1550 nm. In one example, when
the outer cladding is essentially pure silica, n.sub.SiO2=1.444 at
a wavelength of 1550 nm.
[0078] In the description that follows, the relative refractive
index (also referred herein as the "relative refractive index
percent" for short) is represented by .DELTA. (or "delta"), .DELTA.
% (or "delta %"), or %, all of which can be used interchangeably,
and its values are given in units of percent or %, unless otherwise
specified. Relative refractive index is also expressed as
.DELTA.(r) or .DELTA.(r) %.
[0079] In some embodiments, the bare optical fiber includes a
region with a refractive index less than the reference index
n.sub.cl, which means that the relative refractive index percent of
the region is negative. In other embodiments, the bare optical
fiber includes a region with a refractive index greater than the
reference index n.sub.cl, which means that the relative refractive
index percent of the region is positive. In some embodiments, the
bare optical fiber includes a region with a negative relative
refractive index percent and a region with a positive relative
refractive index percent. The minimum relative refractive index of
a region corresponds to the point in the region at which the
relative refractive index is lowest. The maximum relative
refractive index of a region corresponds to the point in the region
at which the relative refractive index is greatest. Depending on
the relative refractive index profile and on the region, each of
the minimum relative refractive index and the maximum relative
refractive index may be positive or negative.
[0080] In some embodiments, the term "dopant" refers to a substance
that changes the relative refractive index of glass relative to
pure un-doped SiO.sub.2. In some embodiments, one or more other
substances that are not updopants may be present in a region of an
optical fiber (e.g., the core) having a positive relative
refractive index .DELTA.. That is, in some embodiments, the core
includes an updopant and a downdopant and has a net relative
refractive index that is positive. In some embodiments, the dopants
used to form the core of the optical fiber disclosed herein include
GeO.sub.2 (germania), Al.sub.2O.sub.3 (alumina), and the like.
Dopants that increase the relative refractive index of glass
relative to pure un-doped SiO.sub.2 are referred to as up-dopants
and dopants that decrease the relative refractive index of glass
relative to pure un-doped SiO.sub.2 are referred to as
down-dopants. Glass that contains an up-dopant is said to be
"up-doped" relative to pure un-doped SiO.sub.2 and glass that
contains a down-dopant is said to be "down-doped" relative to pure
un-doped SiO.sub.2. When the undoped glass is silica glass,
updopants include Cl, Br, Ge, Al, P, Ti, Zr, Nb, Ta, and oxides
thereof, and downdopants include F and B. When comparing two doped
glasses (or two doped regions of a bare optical fiber), the doped
glass (or glass region) having the higher relative refractive index
is said to be up-doped relative to the doped glass (or glass
region) having a lower relative refractive index and the doped
glass (or glass region) having the lower relative refractive index
is said to be down-doped relative to the doped glass (or glass
region) having the higher relative refractive index. Glass regions
of constant refractive index may be formed by not doping or by
doping at a uniform concentration over the thickness of the region.
Regions of variable refractive index are formed through non-uniform
spatial distributions of dopants over the thickness of a region
and/or through incorporation of different dopants in different
portions of a region.
[0081] In some embodiments, the relative refractive index of a
region is an .alpha.-profile defined by a parameter .alpha.. The
parameter .alpha. (also called the "profile parameter" or "alpha
parameter") relates to the relative refractive .DELTA.(r) of a
region through the equation:
.DELTA.(r)=.DELTA..sub.0{1-[(r-r.sub.m)/(r.sub.0-r.sub.m)].sup..alpha.}
where r.sub.m is the point where .DELTA.(r) is the maximum
.DELTA..sub.0, r.sub.0 is the point at which .DELTA.(r) reaches a
minimum value and r is in the range r.sub.i to r.sub.f, where
.DELTA.(r) is defined above, r.sub.i is the initial point of the
.alpha.-profile, r.sub.f is the final point of the .alpha.-profile
and .alpha. is an exponent that is a real number. In one example,
r.sub.0 is the point at which .DELTA.(r)=0. At low values of
.alpha., the .alpha.-profile is a graded index profile. As the
value of a increases, the .alpha.-profile more closely resembles a
step index profile. For purposes of the present disclosure, an
.alpha.-profile with .alpha.>10 is regarded as a step index
relative refractive profile and an .alpha.-profile with
.alpha.<10 is regarded as a graded relative refractive index
profile.
[0082] The "trench volume" is denoted by V.sub.Trench and is
defined as
V Trench = 2 .intg. T Trench , inner T Trench , outer ( .DELTA.
Trench ( r ) - .DELTA. 4 ) rdr ##EQU00003##
where r.sub.Trench,inner is the inner radius of the trench region
of the refractive index profile, r.sub.Trench,outer is the outer
radius of the trench region of the refractive index profile,
.DELTA..sub.4 is the relative refractive index of the outer
cladding region that surrounds and is directly adjacent to the
trench region, and .DELTA..sub.Trench(r) is the relative refractive
index of the trench, where .DELTA..sub.Trench(r)<.DELTA..sub.4
at all radial positions between r.sub.Trench,inner and
r.sub.Trench,outer. In one embodiment, the trench region is an
inner cladding region and r.sub.Trench,inner is r.sub.1,
r.sub.Trench,outer is r.sub.2, and .DELTA..sub.Trench is
.DELTA..sub.2. In another embodiment, the trench region is a
depressed index cladding region and r.sub.Trench,inner is r.sub.2,
r.sub.Trench,outer is r.sub.3, and .DELTA..sub.Trench is
.DELTA..sub.3. Trench volume is defined as an absolute value and
has a positive value. Trench volume is expressed herein in units of
% .DELTA.micron.sup.2, % .DELTA.-micron.sup.2, %
.DELTA.-.mu.m.sup.2, or % .DELTA..mu.m.sup.2, whereby these units
can be used interchangeably herein.
[0083] The "mode field diameter" or "MFD" of an optical fiber is
determined using the Peterman II method, which is the current
international standard measurement technique for measuring the MFD
of an optical fiber. The MFD is given by:
M F D = 2 w w = [ 2 .intg. 0 .infin. ( f ( r ) ) 2 r d r .intg. 0
.infin. ( d f ( r ) d r ) 2 r d r ] 1 / 2 ##EQU00004##
where f(r) is the transverse component of the electric field
distribution of the guided optical signal and r is radial position
in the fiber. The MFD depends on the wavelength of the optical
signal and is reported for selected embodiments herein at
wavelengths of 1310 nm and/or 1550 nm.
[0084] The "effective area" of an optical fiber is defined as:
A eff = 2 .pi. [ .intg. 0 .infin. ( f ( r ) ) 2 r d r ] 2 .intg. 0
.infin. ( f ( r ) ) 4 r d r ##EQU00005##
where f(r) is the transverse component of the electric field of the
guided optical signal and r is radial position in the fiber. In
some embodiment, the effective area" or "A.sub.eff" depends on the
wavelength of the optical signal and is understood to refer to
wavelengths of 1310 nm and 1550 nm as indicated herein.
[0085] The zero-dispersion wavelength is denoted .lamda..sub.0 and
is the wavelength for a single mode fiber at which material
dispersion and waveguide dispersion cancel. In some embodiments, in
silica-based optical fibers, the zero-dispersion wavelength is
about 1310 nm, e.g., between 1300 nm and 1320 nm, depending on the
dopants and refractive index profile used to form the optical
fiber. Dispersion slope is the rate of change of dispersion with
respect to wavelength. Dispersion and dispersion slope are reported
for selected embodiments herein at a wavelength of 1310 nm and/or
1550 nm. Dispersion and dispersion slope are expressed in units of
ps/nm-km and ps/nm.sup.2-km, respectively.
[0086] The cutoff wavelength of an optical fiber is the minimum
wavelength at which the optical fiber will support only one
propagating mode. For wavelengths below the cutoff wavelength,
multimode transmission may occur and an additional source of
dispersion (intermodal dispersion) may arise to limit the fiber's
information carrying capacity. Cutoff wavelength will be reported
herein as a fiber cutoff wavelength (.lamda..sub.CF) or a cable
cutoff wavelength (.lamda..sub.CC). The 22-meter cable cutoff
wavelength is typically less than the 2-meter cutoff wavelength due
to higher levels of bending and mechanical pressure in the cable
environment. The fiber cutoff wavelength .lamda..sub.CF is based on
a 2-meter fiber length while the cable cutoff wavelength
.lamda..sub.CC is based on a 22-meter cabled fiber length as
specified in TIA-455-80: FOTP-80 IEC-60793-1-44 Optical
Fibres--Part 1-44: Measurement Methods and Test Procedures--Cut-off
Wavelength (21 May 2003), by Telecommunications Industry
Association (TIA).
[0087] The optical fibers disclosed herein include a core region, a
cladding region directly adjacent to and surrounding the core
region, and a coating directly adjacent to and surrounding the
cladding region. The cladding region is a single homogeneous region
or multiple regions that differ in relative refractive index. The
multiple cladding regions are preferably concentric regions.
[0088] In some embodiments, the cladding region includes an inner
cladding region and an outer cladding region directly adjacent to
and surrounding the inner cladding region. The relative refractive
index of the inner cladding region may be greater than, equal to,
or less than the relative refractive index of the outer cladding
region. An inner cladding region having a lower refractive index
than the outer cladding region is referred to herein as a trench or
trench region.
[0089] In some embodiments, the cladding region includes a
depressed index cladding region between and directly adjacent to an
inner cladding region and an outer cladding region. The depressed
index cladding region is a cladding region having a lower relative
refractive index than the inner cladding and the outer cladding
region. The depressed index cladding region may also be referred to
herein as a trench or trench region. The depressed index cladding
region surrounds and is directly adjacent to the inner cladding
region. The depressed index cladding region is surrounded by and
directly adjacent to an outer cladding region. The depressed index
cladding region may contribute to a reduction in bending
losses.
[0090] The core region, inner cladding region, depressed index
cladding region, and outer cladding region are also referred to as
core, inner cladding, depressed index cladding, and outer cladding,
respectively. The inner cladding, depressed index cladding and
outer cladding may independently have a positive or negative
relative refractive index. The core preferably has a positive
relative refractive index. Preferred values for relative refractive
index for each of the regions are given below.
[0091] Whenever used herein, radial position r.sub.1 and relative
refractive index .DELTA..sub.1 or .DELTA..sub.1(r) refer to the
core region, radial position r.sub.2 and relative refractive index
.DELTA..sub.2 or .DELTA..sub.2(r) refer to the inner cladding
region, radial position r.sub.3 and relative refractive index
.DELTA..sub.3 or .DELTA..sub.3(r) refer to the depressed index
cladding region, radial position r.sub.4 and relative refractive
index .DELTA..sub.4 or .DELTA..sub.4(r) refer to the outer cladding
region, radial position r.sub.5 refers to the primary coating,
radial position r.sub.6 refers to the secondary coating, and radial
position r.sub.7 refers to the optional tertiary coating. Radial
position r.sub.4 and relative refractive index .DELTA..sub.4 or
.DELTA..sub.4(r) will also be used to refer to the cladding region
in embodiments that include a single cladding region instead of
multiple cladding regions.
[0092] The relative refractive index .DELTA..sub.1(r) has a maximum
value .DELTA..sub.1max and a minimum value .DELTA..sub.1min. The
relative refractive index .DELTA..sub.2(r) has a maximum value
.DELTA..sub.2max and a minimum value .DELTA..sub.2 min. The
relative refractive index .DELTA..sub.3(r) has a maximum value
.DELTA..sub.3max and a minimum value .DELTA..sub.3 min. The
relative refractive index .DELTA..sub.4(r) has a maximum value
.DELTA..sub.4max and a minimum value .DELTA..sub.4 min. In
embodiments in which the relative refractive index is constant or
approximately constant over a region, the maximum and minimum
values of the relative refractive index are equal or approximately
equal. Unless otherwise specified, if a single value is reported
for the relative refractive index of a region, the single value
corresponds to an average value for the region.
[0093] It is understood that the central core region is
substantially cylindrical in shape and that a surrounding inner
cladding region, a surrounding depressed index cladding region, a
surrounding outer cladding region, a surrounding primary coating, a
surrounding secondary coating, and a surrounding tertiary coating
are substantially annular in shape. Annular regions are
characterized in terms of an inner radius and an outer radius.
Radial positions r.sub.1, r.sub.2, r.sub.3, r.sub.4, r.sub.5,
r.sub.6, and r.sub.7 refer herein to the outermost radii of the
core, inner cladding, depressed index cladding, outer cladding,
primary coating, secondary coating, and tertiary coating,
respectively. In embodiments having a single cladding instead of
multiple cladding regions, r.sub.4 refers to the outermost radius
of the cladding. The radius r.sub.6 corresponds to the outer radius
of the optical fiber in embodiments without a tertiary coating.
When a tertiary coating is present, the radius r.sub.7 corresponds
to the outer radius of the optical fiber.
[0094] When two regions are directly adjacent to each other, the
outer radius of the inner of the two regions coincides with the
inner radius of the outer of the two regions. In one embodiment,
for example, the fiber includes a depressed index cladding region
surrounded by and directly adjacent to an outer cladding region. In
such an embodiment, the radius r.sub.3 corresponds to the outer
radius of the depressed index cladding region and the inner radius
of the outer cladding region. In embodiments in which the relative
refractive index profile includes a depressed index cladding region
surrounding and directly adjacent to an inner cladding region, the
radial position r.sub.2 corresponds to the outer radius of the
inner cladding region and the inner radius of the depressed index
cladding region. In embodiments in which the relative refractive
index profile includes a depressed index cladding region
surrounding and directly adjacent to the core, the radial position
r.sub.1 corresponds to the outer radius of the core and the inner
radius of the depressed index cladding region. In embodiments
having a single cladding region surrounding and directly adjacent
to the core, the radial position r.sub.1 corresponds to the outer
radius of the core and the inner radius of the cladding region.
[0095] The following terminology applies to embodiments in which
the relative refractive index profile includes an inner cladding
region surrounding and directly adjacent to the core, a depressed
index cladding region surrounding and directly adjacent to the
inner cladding region, an outer cladding region surrounding and
directly adjacent to the depressed index cladding region, a primary
coating surrounding and directly adjacent to the outer cladding
region, and a secondary coating surrounding and directly adjacent
to the primary coating. The difference between radial position
r.sub.2 and radial position r.sub.1 is referred to herein as the
thickness of the inner cladding region. The difference between
radial position r.sub.3 and radial position r.sub.2 is referred to
herein as the thickness of the depressed index cladding region. The
difference between radial position r.sub.4 and radial position
r.sub.3 is referred to herein as the thickness of the outer
cladding region. The difference between radial position r.sub.5 and
radial position r.sub.4 is referred to herein as the thickness of
the primary coating. The difference between radial position r.sub.6
and radial position r.sub.5 is referred to herein as the thickness
of the secondary coating.
[0096] The following terminology applies to embodiments in which an
inner cladding region is directly adjacent to a core region and an
outer cladding region is directly adjacent the inner cladding
region. The difference between radial position r.sub.2 and radial
position r.sub.1 is referred to herein as the thickness of the
inner cladding region. The difference between radial position
r.sub.4 and radial position r.sub.2 is referred to herein as the
thickness of the outer cladding region. The difference between
radial position r.sub.5 and radial position r.sub.4 is referred to
herein as the thickness of the primary coating. The difference
between radial position r.sub.6 and radial position r.sub.5 is
referred to herein as the thickness of the secondary coating.
[0097] The following terminology applies to embodiments in which
the relative refractive index profile lacks both an inner cladding
region and a depressed index cladding region. The difference
between radial position r.sub.4 and radial position r.sub.1 is
referred to herein as the thickness of the cladding region. The
difference between radial position r.sub.5 and radial position
r.sub.4 is referred to herein as the thickness of the primary
coating. The difference between radial position r.sub.6 and radial
position r.sub.5 is referred to herein as the thickness of the
secondary coating.
[0098] The coatings described herein are formed from curable
coating compositions. Curable coating compositions include one or
more curable components. As used herein, the term "curable" is
intended to mean that the component, when exposed to a suitable
source of curing energy, includes one or more curable functional
groups capable of forming covalent bonds that participate in
linking the component to itself or to other components of the
coating composition. The product obtained by curing a curable
coating composition is referred to herein as the cured product of
the composition. The cured product is preferably a polymer. The
curing process is induced by energy. Forms of energy include
radiation or thermal energy. In a preferred embodiment, curing
occurs with radiation, where radiation refers to electromagnetic
radiation. Curing induced by radiation is referred to herein as
radiation curing or photocuring. A radiation-curable component is a
component that can be induced to undergo a curing reaction when
exposed to radiation of a suitable wavelength at a suitable
intensity for a sufficient period of time. Suitable wavelengths
include wavelengths in the infrared, visible, or ultraviolet
portion of the electromagnetic spectrum. The radiation curing
reaction occurs in the presence of a photoinitiator. A
radiation-curable component may also be thermally curable.
Similarly, a thermally curable component is a component that can be
induced to undergo a curing reaction when exposed to thermal energy
of sufficient intensity for a sufficient period of time. A
thermally curable component may also be radiation curable.
[0099] A curable component includes one or more curable functional
groups. A curable component with only one curable functional group
is referred to herein as a monofunctional curable component. A
curable component having two or more curable functional groups is
referred to herein as a multifunctional curable component.
Multifunctional curable components include two or more functional
groups capable of forming covalent bonds during the curing process
and can introduce crosslinks into the polymeric network formed
during the curing process. Multifunctional curable components may
also be referred to herein as "crosslinkers" or "curable
crosslinkers". Curable components include curable monomers and
curable oligomers. Examples of functional groups that participate
in covalent bond formation during the curing process are identified
hereinafter.
[0100] The term "molecular weight" when applied to polyols means
number average molecular weight (M.sub.n).
[0101] The term "(meth)acrylate" means methacrylate, acrylate, or a
combination of methacrylate and acrylate.
[0102] Values of Young's modulus, % elongation, and tear strength
refer to values as determined under the measurement conditions by
the procedures described herein.
[0103] Reference will now be made in detail to illustrative
embodiments of the present description.
[0104] The present description relates to curable coating
compositions, coatings formed from the curable coating
compositions, and coated articles coated or encapsulated by the
coating obtained by curing the curable coating compositions. In a
preferred embodiment, the curable coating composition is a
composition for forming coatings for optical fibers, the coating is
an optical fiber coating, and the coated article is a coated
optical fiber. The present description also relates to methods of
making curable coating compositions, methods of forming coatings
from the curable coating compositions, and methods of coating
fibers with the curable coating composition.
[0105] One aspect of the present disclosure relates to an optical
fiber. FIG. 1 is a schematic elevated view of a section of an
example optical fiber 100 according to some embodiments. In some
embodiments, the optical fiber 100 has a centerline AC shown by way
of example as running in the z-direction. The optical fiber 100
comprises a glass core region ("core") 10 that is centered on the
centerline AC. The core 10 can be immediately is surrounded by and
directly adjacent to a glass cladding region ("cladding") 50. The
cladding 50 is surrounded by and directly adjacent to a protective
coating 70 made of a non-glass material, such as a polymeric
material. In some embodiments, the optical fiber 100 can have a
diameter r.sub.6 or r.sub.7 of less than or equal to 230 microns
(e.g., .ltoreq.210 microns, .ltoreq.200 microns, .ltoreq.180
microns, .ltoreq.165 microns, .ltoreq.130 microns, .ltoreq.110
microns, etc.).
[0106] Referring to FIG. 2, a cross-sectional view of an exemplary
optical fiber 100 in x-y plane is shown in accordance with some
embodiments of the present disclosure.
[0107] As illustrated, the core 10 has a radius r.sub.1 and a
relative refractive index .DELTA..sub.1. The cladding 50 can be
directly adjacent to and surrounding the core 10. In some
embodiments, the cladding 50 includes an inner cladding region
("inner cladding") 52 directly adjacent to and surrounding the core
10, a depressed index cladding region ("depressed index cladding")
54 directly adjacent to and surrounding the inner cladding 52, and
an outer cladding region ("outer cladding") 56 directly adjacent to
and surrounding the depressed index cladding 54. The inner cladding
52 extends from the radius r.sub.1 to a radius r.sub.2 and has a
relative refractive index .DELTA..sub.2. The depressed index
cladding 54 extends from the radius r.sub.2 to a radius r.sub.3 and
has a relative refractive index .DELTA..sub.3. The outer cladding
56 extends from the radius r.sub.3 to a radius r.sub.4 and has a
relative refractive index .DELTA..sub.4.
[0108] In some alternative embodiments not shown in the figures,
the depressed index cladding 54 can be omitted. That is, the
cladding 50 includes only two cladding regions. The inner cladding
52 can be directly adjacent to and surrounding the core 10, and
extend from the radius r.sub.1 to a radius r.sub.2 and have a
relative refractive index .DELTA..sub.2. The outer cladding 56 can
be directly adjacent to and surrounding the inner cladding 52, and
extend from the radius r.sub.2 to a radius r.sub.4 and have a
relative refractive index .DELTA..sub.4.
[0109] In some other alternative embodiments not shown in the
figures, the inner cladding 52 and the depressed index cladding 54
can be omitted. That is, the cladding 50 includes only one cladding
region. The outer cladding 56 can be directly adjacent to and
surrounding the core 10, and extend from the radius r.sub.1 to a
radius r.sub.4 and have a relative refractive index
.DELTA..sub.4.
[0110] Protective coating 70 is directly adjacent to and surrounds
the cladding 50. In some embodiments, the protective coating 70
includes a primary coating 72 and a secondary coating 74. The
primary coating 72 and the secondary coating 74 are typically
formed by applying a curable coating composition to the glass fiber
as a viscous liquid and curing. In some embodiments, the protective
coating 70 may also include a tertiary coating 76 that surrounds
the secondary coating 74.
[0111] The secondary coating 74 is a harder material (higher
Young's modulus) than the primary coating 72 and is designed to
protect the glass fiber from damage caused by abrasion or external
forces that arise during processing, handling, and installation of
the optical fiber. The primary coating 72 is a softer material
(lower Young's modulus) than the secondary coating 74 and is
designed to buffer or dissipates stresses that result from forces
applied to the outer surface of the secondary coating 74.
[0112] The primary coating 72 dissipates shear forces and minimizes
the stress that reaches the glass fiber (which includes the core 10
and the cladding 50). The primary coating 72 is especially
important in dissipating shear forces that arise due to the
microbends that the optical fiber encounters when deployed in a
cable.
[0113] The primary coating 72 should maintain adequate adhesion to
the glass fiber during thermal and hydrolytic aging, yet be
strippable from the glass fiber for splicing purposes.
[0114] The optional tertiary coating 76 may include pigments, inks
or other coloring agents to mark the optical fiber for
identification purposes and typically has a Young's modulus similar
to the Young's modulus of the secondary coating 74.
[0115] Another aspect of the present disclosure relates to an
optical fiber ribbon. FIG. 3 illustrates a cross-sectional view of
an exemplary optical fiber ribbon 300 in accordance with some
embodiments of the present disclosure. As illustrated, the optical
fiber ribbon 300 includes a plurality of optical fibers 100 and a
matrix 320 encapsulating the plurality of optical fibers 100. Each
optical fiber 100 includes a core, a cladding, and a protective
coating as described above. The ribbon matrix 320 can be formed
from the same composition used to prepare a secondary coating, or
the ribbon matrix 320 can be formed from a different composition
that is otherwise compatible for use.
[0116] The optical fibers 100 are aligned relative to one another
in a substantially planar and parallel relationship. The optical
fibers 100 in the optical fiber ribbon 300 are encapsulated by the
ribbon matrix 320 in any suitable configuration (e.g., edge-bonded
ribbon, thin-encapsulated ribbon, thick-encapsulated ribbon, or
multi-layer ribbon) by any suitable fabricating methods. In FIG. 3,
the fiber optic ribbon 300 contains twelve (12) optical fibers 100;
however, it should be apparent to those skilled in the art that any
number of optical fibers 100 (e.g., two or more) may be employed to
form fiber optic ribbon 300 disposed for a particular use.
[0117] Another aspect of the present disclosure relates to an
optical fiber cable. FIG. 4 illustrates a cross-sectional view of
an exemplary optical fiber cable 400. Cable 400 includes a
plurality of optical fibers 100 surrounded by jacket 430. Optical
fibers 100 may be densely or loosely packed into a conduit enclosed
by inner surface of jacket 430. The number of fibers placed in the
jacket 430 is referred to as the "fiber count" of optical fiber
cable 400. The jacket 430 is formed from an extruded polymer
material and may include multiple concentric layers of polymers or
other materials. Optical fiber cable 400 may include one or more
strengthening members (not shown) embedded within jacket 430 or
placed within the conduit defined by the inner surface of jacket
430. Strengthening members include fibers or rods that are more
rigid than jacket 430. The strengthening member is made from metal,
braided steel, glass-reinforced plastic, fiberglass, or other
suitable material. Optical fiber cable 400 may include other layers
surrounded by jacket 430 (e.g. armor layers, moisture barrier
layers, rip cords, etc.). Optical fiber cable 400 may have a
stranded, loose tube core or other fiber optic cable
construction.
[0118] Relative Refractive Index Profiles
[0119] In some embodiments, the optical fiber 100 can have a number
of different physical configurations defined by way of example as a
relative refractive index profile. One type of the disclosed
optical fiber is a graded-index fiber, which has a core region with
a refractive index that varies with distance from the fiber center.
Examples of graded-index fibers include fibers having a core with a
relative refractive index having an .alpha.-profile defined above
or a super-Gaussian relative refractive index profile. Examples of
the graded-index fibers are set forth below in connection with
FIGS. 5A-5C. Another type of the disclosed optical fiber is a
step-index fiber, which has a core region with a step index
relative refractive index profile. Examples of the step-index
fibers are set forth below in connection with FIGS. 6A-6E.
[0120] Referring to FIG. 5A, a plot of the relative refractive
index .DELTA. %(r) versus the radial coordinate illustrating a
first exemplary physical configuration of a graded-index fiber,
according to some embodiments. As shown, the core 10 having a
radius r.sub.1 can have a graded refractive index defined by
described by an .alpha.-profile. The radial position r.sub.0
(corresponding to .DELTA..sub.1max) of the .alpha.-profile
corresponds to the centerline AC (r=0) of the fiber and the radial
position r.sub.z of the .alpha.-profile corresponds to the core
radius r.sub.1. In some embodiments with a centerline dip, the
radial position r.sub.0 is slightly offset from the centerline AC
of the fiber.
[0121] In some embodiments, the core 10 is immediately surrounded
by the cladding 50 that extends from the radius r.sub.1 out to a
radius r.sub.4. The cladding 50 can include an inner cladding
region 52 and an outer cladding region 56 surrounding the inner
cladding region 52. The inner cladding region 52 can be a pure
silica cladding or a cladding comprised essentially of SiO.sub.2
extending from the radius r.sub.1 to a radius r.sub.2 and having a
relative refractive index .DELTA..sub.2 that is substantially zero.
The outer cladding region 54 can be an up-doped cladding extending
from the radius r.sub.2 to the radius r.sub.4, and having a
relative refractive index .DELTA..sub.4, wherein
.DELTA..sub.2.ltoreq..DELTA..sub.4<.DELTA..sub.1max.
[0122] FIG. 5B is a plot of the relative refractive index .DELTA.
%(r) versus the radial coordinate illustrating a second exemplary
physical configuration of a graded-index fiber, according to some
embodiments. The core 10 having a radius r.sub.1 can have a graded
refractive index defined by described by an .alpha.-profile. The
core 10 is immediately surrounded by the cladding 50 that extends
from the radius r.sub.1 out to a radius r.sub.4. The cladding 50
includes an inner cladding region 52 and an outer cladding region
56 surrounding the inner cladding region 52. The inner cladding
region 52 can be a down-doped cladding extending from the radius
r.sub.1 to a radius r.sub.2 and having a negative relative
refractive index .DELTA..sub.2. The outer cladding region 54 can be
a pure silica cladding or a cladding comprised essentially of
SiO.sub.2 extending from the radius r.sub.2 to the radius r.sub.4,
and having a relative refractive index .DELTA..sub.4 that is
substantially zero.
[0123] FIG. 5C is a plot of the relative refractive index .DELTA.
%(r) versus the radial coordinate illustrating a third exemplary
physical configuration of a graded-index fiber, according to some
embodiments. The core 10 having a radius r.sub.1 can have a graded
refractive index defined by described by an .alpha.-profile. The
core 10 is immediately surrounded by the cladding 50 that extends
from the radius r.sub.1 out to a radius r.sub.4. The cladding 50
includes an inner cladding region 52, a depressed index cladding 54
directly adjacent to and surrounding the inner cladding 52, and an
outer cladding region 56 surrounding the inner cladding region 52.
The inner cladding region 52 can be a pure silica cladding or a
cladding comprised essentially of SiO.sub.2 extending from the
radius r.sub.1 to a radius r.sub.2 and having a negative relative
refractive index .DELTA..sub.2. The depressed index cladding 54 can
be a down-doped cladding extending from the radius r.sub.2 to a
radius r.sub.3 and having a negative relative refractive index
.DELTA..sub.3. The outer cladding region 54 can be a pure silica
cladding or a cladding comprised essentially of SiO.sub.2 extending
from the radius r.sub.3 to the radius r.sub.4, and having a
relative refractive index .DELTA..sub.4 that is substantially
zero.
[0124] Referring to FIG. 6A, a first exemplary physical
configuration of a step-index fiber is illustrated in the form of a
plot of the relative refractive index .DELTA. %(r) versus the
radial coordinate r, according to some embodiments. As shown, the
core 10 can be a step refractive index core having a radius r.sub.1
and a relative refractive index .DELTA..sub.1. The core 10 is
immediately surrounded by the cladding 50. The cladding 50 can be a
pure silica cladding or a cladding comprised essentially of
SiO.sub.2. The cladding 50 can extend from the radius r.sub.1 out
to a radius r.sub.4 and having a relative refractive index
.DELTA..sub.4 that is substantially zero.
[0125] FIG. 6B is another plot of the relative refractive index
.DELTA. %(r) versus the radial coordinate illustrating a second
exemplary physical configuration of a step-index fiber, according
to some embodiments. Similarly, the core 10 can be a step
refractive index core having a radius r.sub.1 and a relative
refractive index .DELTA..sub.1. The core 10 is immediately
surrounded by the cladding 50 that extends from the radius r.sub.1
out to a radius r.sub.4. The cladding 50 can be down-doped with a
negative relative refractive index .DELTA..sub.4.
[0126] FIG. 6C is another plot of the relative refractive index
.DELTA. %(r) versus the radial coordinate illustrating a third
exemplary physical configuration of a step-index fiber, according
to some embodiments. The core 10 can be a step refractive index
core having a radius r.sub.1 and a relative refractive index
.DELTA..sub.1. The core 10 is immediately surrounded by the
cladding 50 that extends from the radius r.sub.1 out to a radius
r.sub.4. The cladding 50 can include an inner cladding region 52
and an outer cladding region 56 surrounding the inner cladding
region 52. The inner cladding region 52 can be a pure silica
cladding or a cladding comprised essentially of SiO.sub.2 extending
from the radius r.sub.1 to a radius r.sub.2 and having a relative
refractive index .DELTA..sub.2 that is substantially zero. The
outer cladding region 56 can be an up-doped cladding extending from
the radius r.sub.2 to the radius r.sub.4, and having a relative
refractive index .DELTA..sub.4, wherein
.DELTA..sub.2<.DELTA..sub.4<i.
[0127] FIG. 6D is another plot of the relative refractive index
.DELTA. %(r) versus the radial coordinate illustrating a fourth
exemplary physical configuration of a step-index fiber, according
to some embodiments. The core 10 can be a step refractive index
core having a radius r.sub.1 and a relative refractive index
.DELTA..sub.1. The core 10 is immediately surrounded by the
cladding 50 that extends from the radius r.sub.1 out to a radius
r.sub.4. The cladding 50 can include an inner cladding region 52
and an outer cladding region 56 surrounding the inner cladding
region 52. The inner cladding region 52 can be a down-doped
cladding with a negative relative refractive index .DELTA..sub.2.
The outer cladding region 56 can be a pure silica cladding or a
cladding comprised essentially of SiO.sub.2 extending from the
radius r.sub.2 to the radius r.sub.4, and having a relative
refractive index .DELTA..sub.4 that is substantially zero.
[0128] FIG. 6E is another plot of the relative refractive index
.DELTA. %(r) versus the radial coordinate illustrating a fifth
exemplary physical configuration of a step-index fiber, according
to some embodiments. The core 10 can be a step refractive index
core having a radius r.sub.1 and a relative refractive index
.DELTA..sub.1. The core 10 is immediately surrounded by the
cladding 50 that extends from the radius r.sub.1 out to a radius
r.sub.4. The cladding 50 can include an inner cladding region 52
and an outer cladding region 56 surrounding the inner cladding
region 52. The inner cladding region 52 can be a down-doped
cladding with a negative relative refractive index .DELTA..sub.2.
The outer cladding region 56 can be a lightly down-doped cladding
with a negative relative refractive .DELTA..sub.4 larger than
.DELTA..sub.2, wherein
.DELTA..sub.2.ltoreq..DELTA..sub.4<.DELTA..sub.1.
[0129] In other embodiments (not illustrated), a fiber with a
step-index relative refractive index profile for the core has a
cladding that includes an inner cladding region surrounded by a
depressed-index cladding region, which is surrounded by an outer
cladding region. For example, any of the step-index profiles
depicted in FIGS. 6C-6E can be modified to include a
depressed-index cladding region 54 between the inner cladding
region 52 and the outer cladding region 54 (see, for example, the
cladding region 50 shown in FIG. 5C).
[0130] It is to be understood that, in the above FIGS. 5A-5C and
FIGS. 6A-6E, the relative refractive index transitions between
adjacent regions shown as step changes are idealization for
illustrative purpose and may not be strictly vertical in practice.
Instead, the relative refractive index transitions between adjacent
regions may have a slope or curvature. When the relative refractive
index transitions between adjacent regions are non-vertical, the
corresponding boundaries (radius) between adjacent regions are
defined by the mid-points of the relative refractive index
transition regions between the adjacent regions.
[0131] Parameter Specifications of Properties
[0132] In some embodiments, various fiber parameters described
herein can be properly designed to increase transmission capacity,
puncture resistance and microbending performance. In the following,
details of various designs of the fiber parameters are described
below. It is noted that, the following numerical values for fiber
parameters can be applied to fibers with either step index cores or
graded index cores described, for example, above in connection with
FIGS. 5A-5C and 6A-6E.
[0133] In various embodiments, the outer radius r.sub.1 of the core
is in a range from 3.0 microns to 10.0 microns, or in a range from
4.0 microns to 9.0 microns, or in a range from 5.0 microns to 8.0
microns, or in a range from 5.0 microns to 9.0 microns, or in a
range from 6.0 microns to 9.0 microns. In some embodiments, the
relative refractive index of the core is described by a step-index
profile having a constant or approximately constant value
corresponding to .DELTA..sub.1 in a range from 0.08% to 0.450%, or
in a range from 0.10% to 0.40%, or in a range from 0.12% to 0.35%,
or in a range from 0.14% to 0.30%. In some other embodiments, the
relative refractive index of the core is described by an
.alpha.-profile with an .alpha. value in a range from 1 to 200, or
in a range from 5 to 150, or in a range from 10 to 100, or in a
range from 5 to 10, or greater than 5, or greater than 10, or
greater than 20, or less than 20, or less than 10, or less than 5.
The corresponding maximum relative refractive index
.DELTA..sub.1max of the core region is in a range from 0.08% to
0.45%, or in a range from 0.10% to 0.40%, or in a range from 0.12%
to 0.35%, or in a range from 0.14% to 0.30%. In some embodiments,
the core can be doped with chlorine ("Cl-doped" hereinafter), with
the chlorine concentration in a range from 1.5 wt % to 6.0 wt %, or
in a range from 2.0 wt % to 5.5 wt %, or in a range from 2.5 wt %
to 5.0 wt %, or in a range from 3.0 wt % to 4.5 wt %, or greater
than or equal to 1.5 wt % (e.g., .gtoreq.2 wt %, .gtoreq.2.5 wt %,
.gtoreq.3 wt %, .gtoreq.3.5 wt %, .gtoreq.4 wt %, .gtoreq.4.5 wt %,
.gtoreq.5 wt %, etc.) It is noted that, the notation "wt %" used
herein means a weight percentage. It is also noted that, the core
is GeO.sub.2 free, or a concentration of GeO.sub.2 in the cores is
less than 1.0 wt %.
[0134] In various embodiments, a thickness (r.sub.2-r.sub.1) of the
inner cladding is in a range from 1.0 microns to 7.0 microns, or in
a range from 2.0 microns to 6.0 microns, or in a range from 3.0
microns to 5.5 microns, or in a range from 3.5 microns to 5.0
microns. The relative refractive index .DELTA..sub.2 of the inner
cladding is in a range from -0.15% to 0.15%, or in a range from
-0.10% to 0.10%, or in a range from -0.05 to 0.05%, or in a range
from -0.15% to 0.0%, or in a range from -0.10% to 0.0%. In some
embodiments, the inner cladding is downdoped. For example, the
inner cladding can be doped with fluorine ("F-doped" hereinafter)
with a fluorine concentration in a range from 0.01 wt % to 0.20 wt
%, or in a range from 0.05 wt % to 0.15 wt %. In some other
embodiments, the inner cladding is updoped. For example, the inner
cladding can be Cl-doped with a chlorine concentration in a range
from 0.01 wt % to 0.50 wt %, or in a range from 0.05 wt % to 0.40
wt %, or in a range from 0.10 wt % to 0.30 wt %.
[0135] The inner radius of the depressed index cladding region is
r.sub.2 and has the values specified above. In various embodiments,
the outer radius r.sub.3 of the depressed index cladding is in a
range from 15 microns to 40 microns, or in a range from 18 microns
to 37 microns, or in a range from 20 microns to 35 microns, or in a
range from 22 microns to 30 microns. The relative refractive index
.DELTA..sub.3 of the depressed index cladding is in a range from
-0.25% to 0.00%, or in a range from -0.20% to -0.05%, or in a range
from -0.20 to -0.10. As described above, the depressed index
cladding is downdoped, such as being F-doped with a fluorine
concentration in a range from 0.10 wt % to 0.50 wt %, or in a range
from 0.15 wt % to 0.45 wt %, or in a range from 0.20 wt % to 0.40
wt %, or greater than 0.10 wt %, or greater than 0.15 wt %, or
greater than 0.20 wt %. A trench volume of the depressed index
cladding is greater than 40% .DELTA.-micron.sup.2, greater than 50%
.DELTA.-micron.sup.2, greater than 60% .DELTA.-micron.sup.2,
greater than 70% .DELTA.-micron.sup.2, or in a range from 40%
.DELTA.-micron.sup.2 to 80% .DELTA.-micron.sup.2, or in a range
from 50% .DELTA.-micron.sup.2 to 70% .DELTA.-micron.sup.2. It is
noted that, in some embodiments, the cladding includes only the
inner cladding and outer cladding without the intervening depressed
index cladding, as described above in connection with FIGS. 5A-5B
and 6C-6E, the inner cladding functions as a depressed index
cladding.
[0136] The inner radius of the outer cladding region is r.sub.3 and
has the values specified above. In various embodiments, the outer
radius r.sub.4 of the outer cladding is greater than 50 microns, or
greater than 55 microns, or greater than 60 microns, or in a range
from 50 microns to 70 microns, or in a range from 55 microns to 65
microns, or in a range from 57 microns to 64 microns, or about 62.5
microns. The relative refractive index .DELTA..sub.4 of the outer
cladding is in a range from -0.20% to 0.10%, or in a range from
-0.15% to 0.10%, or in a range from -0.10 to 0.05%, or in a range
from -0.05% to 0.05%. In some embodiments, the outer cladding is
downdoped, such as being F-doped with a fluorine concentration in a
range from 0.05 wt % to 0.30 wt %, or in a range from 0.10 wt % to
0.25 wt %. In some other embodiments, the outer cladding is
updoped, such as Cl-doped with a chlorine concentration in a range
from 0.10 wt % to 0.60 wt %, or in a range from 0.20 wt % to 0.50
wt %.
[0137] The mode field diameter of the optical fibers disclosed
herein is greater than or equal to 10.0 microns, or greater than or
equal to 11.0 microns, or greater than or equal to 11.5 microns, or
greater than or equal to 12.0 microns, greater than or equal to
13.0 microns, or greater than or equal to 14.0 microns, or in a
range from 10.0 microns to 15 microns, or in a range from 11.0
microns to 14.0 microns at a wavelength of 1550 nm.
[0138] The effective area A.sub.eff of the optical fibers disclosed
herein is greater than 100 micron.sup.2, or greater than 110
micron.sup.2, or greater than 120 micron.sup.2, or greater than 130
micron.sup.2, or greater than 140 micron.sup.2, or greater than 150
micron.sup.2, or in the range from 100 micron.sup.2 to 160
micron.sup.2, or in the range from 110 micron.sup.2 to 150
micron.sup.2, or in the range from 120 micron.sup.2 to 140
micron.sup.2 at a wavelength of 1550 nm.
[0139] The attenuation of the optical fibers disclosed herein is
less than or equal to 0.170 dB/km, or less than or equal to 0.165
dB/km, or less than or equal to 0.160 dB/km, or less than or equal
to 0.155 dB/km, or less than or equal to 0.150 dB/km at a
wavelength of 1550 nm.
[0140] It is noted that, macrobending loss can be determined using
a mandrel wrap test specified in standard IEC 60793-1-47. In the
mandrel wrap test, the optical fiber is wrapped one or more times
around a cylindrical mandrel having a specified diameter, and the
increase in attenuation at a specified wavelength due to the
bending is determined. Attenuation in the mandrel wrap test is
expressed in units of dB/turn, where one turn refers to one
revolution of the optical fiber about the the mandrel. Macrobending
losses at a wavelength of 1550 nm were determined for selected
examples described below with the mandrel wrap test using mandrels
with diameters of ranging from 10 mm to 60 mm. In some embodiments,
the bending loss of the optical fibers at a wavelength of 1550 nm
as determined by the mandrel wrap test using a mandrel having a
diameter of 20 mm can be less than 3.0 dB/turn, or less than 2.5
dB/turn, or less than 2.0 dB/turn, or less than 1.5 dB/turn, or
less than 1.0 dB/turn.
[0141] In some embodiments, the fiber cutoff wavelength CF of the
optical fibers disclosed herein is less than 1530 nm, or less than
1520 nm, or less than 1500 nm, or less than 1450 nm, or less than
1400 nm, or less than 1350 nm, less than 1300 nm, or less than 1260
nm. The 22-meter cable cutoff acc (nm) of the optical fibers
disclosed herein is less than 1530 nm, or less than 1515 nm, or
less than 1490 nm, or less than 1450 nm, or less than 1400 nm, or
less than 1350 nm, less than 1300 nm, or less than 1260 nm, or less
than 1230 nm, or less than 1220 nm.
[0142] In some embodiments the puncture resistance of the optical
fiber 100 can be greater than 30 g (e.g., >40 g, >50 g,
etc.).
[0143] In some embodiments, proper combination of the fiber
parameters in the ranges described above can result in optical
fiber properties that meet the requirements of a high transmission
capacity, a small diameter, a low transmission loss, good
microbending properties, and high puncture resistance. The profiles
designs shown in FIGS. 5A to 5C and 6A to 6E, and the various fiber
parameters described above can be compliant with various optical
fibers, such as ITU G.652.D, G.657.A1, G.657.A2, G.654, etc.
[0144] Optical Fiber Coatings. The transmissivity of light through
an optical fiber is highly dependent on the properties of the
coatings applied to the glass fiber. The coatings typically include
a primary coating and a secondary coating, where the secondary
coating surrounds the primary coating and the primary coating
contacts the glass fiber (which includes a central core region
surrounded by a cladding region). The secondary coating is a harder
material (higher Young's modulus) than the primary coating and is
designed to protect the glass fiber from damage caused by abrasion
or external forces that arise during processing, handling, and
installation of the optical fiber. The primary coating is a softer
material (lower Young's modulus) than the secondary coating and is
designed to buffer or dissipates stresses that result from lateral
forces applied to the outer surface of the secondary coating. The
primary coating is especially important in dissipating stresses
that arise due to the microbends that the optical fiber encounters
when deployed in a cable.
[0145] The primary coating should maintain adequate adhesion to the
glass fiber during thermal and hydrolytic aging, yet be strippable
from the glass fiber for splicing purposes.
[0146] Primary and secondary coatings are typically formed by
applying a curable coating composition to the glass fiber as a
viscous liquid and curing. The optical fiber may also include a
tertiary coating (not shown) that surrounds the secondary coating.
The tertiary coating may include pigments, inks or other coloring
agents to mark the optical fiber for identification purposes and
typically has a Young's modulus similar to the Young's modulus of
the secondary coating.
[0147] Primary Coating Compositions. The primary coating is a cured
product of a curable primary coating composition. The curable
primary coating compositions provide a primary coating for optical
fibers that exhibits low Young's modulus, low pullout force, and
strong cohesion. The curable primary coating compositions further
enable formation of a primary coating that features clean
strippability and high resistance to defect formation during the
stripping operation. Low pullout force facilitates clean stripping
of the primary coating with minimal residue and strong cohesion
inhibits initiation and propagation of defects in the primary
coating when it is subjected to stripping forces. Even for optical
fibers with reduced primary coating thicknesses, the optical fibers
are expected to have low loss and low microbend loss performance.
The primary coatings exhibit these advantages even at reduced
thickness.
[0148] The primary coating is a cured product of a
radiation-curable primary coating composition that includes an
oligomer, a monomer, a photoinitiator and, optionally, an additive.
The following disclosure describes oligomers for the
radiation-curable primary coating compositions, radiation-curable
primary coating compositions containing at least one of the
oligomers, cured products of the radiation-curable primary coating
compositions that include at least one of the oligomers, glass
fibers coated with a radiation-curable primary coating composition
containing at least one of the oligomers, and glass fibers coated
with the cured product of a radiation-curable primary coating
composition containing at least one of the oligomers.
[0149] The oligomer preferably includes a polyether urethane
diacrylate compound and a di-adduct compound. In one embodiment,
the polyether urethane diacrylate compound has a linear molecular
structure. In one embodiment, the oligomer is formed from a
reaction between a diisocyanate compound, a polyol compound, and a
hydroxy acrylate compound, where the reaction produces a polyether
urethane diacrylate compound as a primary product (majority
product) and a di-adduct compound as a byproduct (minority
product). The reaction forms a urethane linkage upon reaction of an
isocyanate group of the diisocyanate compound and an alcohol group
of the polyol. The hydroxy acrylate compound reacts to quench
residual isocyanate groups that are present in the composition
formed from reaction of the diisocyanate compound and polyol
compound. As used herein, the term "quench" refers to conversion of
isocyanate groups through a chemical reaction with hydroxyl groups
of the hydroxy acrylate compound. Quenching of residual isocyanate
groups with a hydroxy acrylate compound converts terminal
isocyanate groups to terminal acrylate groups.
[0150] A preferred diisocyanate compound is represented by formula
(I):
O.dbd.C.dbd.N--R.sub.1--N.dbd.C.dbd.O (I)
which includes two terminal isocyanate groups separated by a
linkage group R.sub.1. In one embodiment, the linkage group R.sub.1
includes an alkylene group. The alkylene group of linkage group
R.sub.1 is linear (e.g. methylene or ethylene), branched (e.g.
isopropylene), or cyclic (e.g. cyclohexylene, phenylene). The
cyclic group is aromatic or non-aromatic. In some embodiments, the
linkage group R.sub.1 is 4,4'-methylene bis(cyclohexyl) group and
the diisocyanate compound is 4,4'-methylene bis(cyclohexyl
isocyanate). In some embodiments, the linkage group R.sub.1 lacks
an aromatic group, or lacks a phenylene group, or lacks an
oxyphenylene group.
[0151] The polyol is represented by molecular formula (II):
##STR00003##
where R.sub.2 includes an alkylene group, to O--R.sub.2-- is a
repeating alkoxylene group, and x is an integer. Preferably, x is
greater than 20, or greater than 40, or greater than 50, or greater
than 75, or greater than 100, or greater than 125, or greater than
150, or in the range from 20 to 500, or in the range from 20 to
300, or in the range from 30 to 250, or in the range from 40 to
200, or in the range from 60 to 180, or in the range from 70 to
160, or in the range from 80 to 140. R.sub.2 is preferably a linear
or branched alkylene group, such as methylene, ethylene, propylene
(normal, iso or a combination thereof), or butylene (normal, iso,
secondary, tertiary, or a combination thereof). The polyol may be a
polyalkylene oxide, such as polyethylene oxide, or a polyalkylene
glycol, such as polypropylene glycol. Polypropylene glycol is a
preferred polyol. The molecular weight of the polyol is greater
than 1000 g/mol, or greater than 2500 g/mol, or greater than 5000
g/mol, or greater than 7500 g/mol, or greater than 10000 g/mol, or
in the range from 1000 g/mol to 20000 g/mol, or in the range from
2000 g/mol to 15000 g/mol, or in the range from 2500 g/mol to 12500
g/mol, or in the range from 2500 g/mol to 10000 g/mol, or in the
range from 3000 g/mol to 7500 g/mol, or in the range from 3000
g/mol to 6000 g/mol, or in the range from 3500 g/mol to 5500 g/mol.
In some embodiments, the polyol is polydisperse and includes
molecules spanning a range of molecular weights such that the
totality of molecules combines to provide the number average
molecular weight specified hereinabove.
[0152] The unsaturation of the polyol is less than 0.25 meq/g, or
less than 0.15 meq/g, or less than 0.10 meq/g, or less than 0.08
meq/g, or less than 0.06 meq/g, or less than 0.04 meq/g, or less
than 0.02 meq/g, or less than 0.01 meq/g, or less than 0.005 meq/g,
or in the range from 0.001 meq/g to 0.15 meq/g, or in the range
from 0.005 meq/g to 0.10 meq/g, or in the range from 0.01 meq/g to
0.10 meq/g, or in the range from 0.01 meq/g to 0.05 meq/g, or in
the range from 0.02 meq/g to 0.10 meq/g, or in the range from 0.02
meq/g to 0.05 meq/g. As used herein, unsaturation refers to the
value determined by the standard method reported in ASTM D4671-16.
In the method, the polyol is reacted with mercuric acetate and
methanol in a methanolic solution to produce acetoxymercuricmethoxy
compounds and acetic acid. The reaction of the polyol with mercuric
acetate is equimolar and the amount of acetic acid released is
determined by titration with alcoholic potassium hydroxide to
provide the measure of unsaturation used herein. To prevent
interference of excess mercuric acetate on the titration of acetic
acid, sodium bromide is added to convert mercuric acetate to the
bromide.
[0153] The reaction to form the oligomer further includes addition
of a hydroxy acrylate compound to react with terminal isocyanate
groups present in unreacted starting materials (e.g. the
diisocyanate compound) or products formed in the reaction of the
diisocyanate compound with the polyol (e.g. urethane compounds with
terminal isocyanate groups). The hydroxy acrylate compound reacts
with terminal isocyanate groups to provide terminal acrylate groups
for one or more constituents of the oligomer. In some embodiments,
the hydroxy acrylate compound is present in excess of the amount
needed to fully convert terminal isocyanate groups to terminal
acrylate groups. The oligomer includes a single polyether urethane
acrylate compound or a combination of two or more polyether
urethane acrylate compounds.
[0154] The hydroxy acrylate compound is represented by molecular
formula (III):
##STR00004##
where R.sub.3 includes an alkylene group. The alkylene group of
R.sub.3 is linear (e.g. methylene or ethylene), branched (e.g.
isopropylene), or cyclic (e.g. phenylene). In some embodiments, the
hydroxy acrylate compound includes substitution of the
ethylenically unsaturated group of the acrylate group. Substituents
of the ethylenically unsaturated group include alkyl groups. An
example of a hydroxy acrylate compound with a substituted
ethylenically unsaturated group is a hydroxy methacrylate compound.
The discussion that follows describes hydroxy acrylate compounds.
It should be understood, however, that the discussion applies to
substituted hydroxy acrylate compounds and in particular to hydroxy
methacrylate compounds.
[0155] In different embodiments, the hydroxy acrylate compound is a
hydroxyalkyl acrylate, such as 2-hydroxyethyl acrylate. The hydroxy
acrylate compound may include water at residual or higher levels.
The presence of water in the hydroxy acrylate compound may
facilitate reaction of isocyanate groups to reduce the
concentration of unreacted isocyanate groups in the final reaction
composition. In various embodiments, the water content of the
hydroxy acrylate compound is at least 300 ppm, or at least 600 ppm,
or at least 1000 ppm, or at least 1500 ppm, or at least 2000 ppm,
or at least 2500 ppm.
[0156] In the foregoing exemplary molecular formulas (I), II), and
(III), the groups R.sub.1, R.sub.2, and R.sub.3 independently are
all the same, are all different, or include two groups that are the
same and one group that is different.
[0157] The diisocyanate compound, hydroxy acrylate compound and
polyol are combined simultaneously and reacted, or are combined
sequentially (in any order) and reacted. In one embodiment, the
oligomer is formed by reacting a diisocyanate compound with a
hydroxy acrylate compound and reacting the resulting product
composition with a polyol. In another embodiment, the oligomer is
formed by reacting a diisocyanate compound with a polyol compound
and reacting the resulting product composition with a hydroxy
acrylate compound.
[0158] The oligomer is formed from a reaction of a diisocyanate
compound, a hydroxy acrylate compound, and a polyol, where the
molar ratio of the diisocyanate compound to the hydroxy acrylate
compound to the polyol in the reaction process is n:m:p. n, m, and
p are referred to herein as mole numbers or molar proportions of
diisocyanate, hydroxy acrylate, and polyol; respectively. The mole
numbers n, m and p are positive integer or positive non-integer
numbers. In embodiments, when p is 2.0, n is in the range from 3.0
to 5.0, or in the range from 3.2 to 4.8, or in the range from 3.4
to 4.6, or in the range from 3.5 to 4.4, or in the range from 3.6
to 4.2, or in the range from 3.7 to 4.0; and m is in the range from
1.5 to 4.0, or in the range from 1.6 to 3.6, or in the range from
1.7 to 3.2, or in the range from 1.8 to 2.8, or in the range from
1.9 to 2.4. For values of p other than 2.0, the molar ratio n:m:p
scales proportionally. For example, the molar ratio
n:m:p=4.0:3.0:2.0 is equivalent to the molar ratio
n:m:p=2.0:1.5:1.0.
[0159] The mole number m may be selected to provide an amount of
the hydroxy acrylate compound to stoichiometrically react with
unreacted isocyanate groups present in the product composition
formed from the reaction of diisocyanate compound and polyol used
to form the oligomer. The isocyanate groups may be present in
unreacted diisocyanate compound (unreacted starting material) or in
isocyanate-terminated urethane compounds formed in reactions of the
diisocyanate compound with the polyol. Alternatively, the mole
number m may be selected to provide an amount of the hydroxy
acrylate compound in excess of the amount needed to
stoichiometrically react with any unreacted isocyanate groups
present in the product composition formed from reaction of the
diisocyanate compound and the polyol. The hydroxy acrylate compound
is added as a single aliquot or multiple aliquots. In one
embodiment, an initial aliquot of hydroxy acrylate is included in
the reaction mixture used to form the oligomer and the product
composition formed can be tested for the presence of unreacted
isocyanate groups (e.g. using FTIR spectroscopy to detect the
presence of isocyanate groups). Additional aliquots of hydroxy
acrylate compound may be added to the product composition to
stoichiometrically react with unreacted isocyanate groups (using,
for example, FTIR spectroscopy to monitor a decrease in a
characteristic isocyanate frequency (e.g. at 2260 cm.sup.-1 to 2270
cm.sup.-1) as isocyanate groups are converted by the hydroxy
acrylate compound). In alternate embodiments, aliquots of hydroxy
acrylate compound in excess of the amount needed to
stoichiometrically react with unreacted isocyanate groups are
added. As described more fully below, for a given value of p, the
ratio of the mole number m to the mole number n influences the
relative proportions of polyether urethane diacrylate compound and
di-adduct compound in the oligomer and differences in the relative
proportions of polyether urethane diacrylate compound and di-adduct
compound lead to differences in the tear strength and/or critical
stress of coatings formed from the oligomer.
[0160] In one embodiment, the oligomer is formed from a reaction
mixture that includes 4,4'-methylene bis(cyclohexyl isocyanate),
2-hydroxyethyl acrylate, and polypropylene glycol in the molar
ratios n:m:p as specified above, where the polypropylene glycol has
a number average molecular weight in the range from 2500 g/mol to
6500 g/mol, or in the range from 3000 g/mol to 6000 g/mol, or in
the range from 3500 g/mol to 5500 g/mol.
[0161] The oligomer preferably includes two components. The first
component is a polyether urethane diacrylate compound having the
molecular formula (IV):
##STR00005##
and the second component is a di-adduct compound having the
molecular formula (V):
##STR00006##
where the groups R.sub.1, R.sub.2, R.sub.3, and the integer x are
as described hereinabove, y is a positive integer, and it is
understood that the group R.sub.1 in molecular formulas (IV) and
(V) is the same as group R.sub.1 in molecular formula (I), the
group R.sub.2 in molecular formula (IV) is the same as group
R.sub.2 in molecular formula (II), and the group R.sub.3 in
molecular formulas (IV) and (V) is the same as group R.sub.3 in
molecular formula (III). The di-adduct compound corresponds to the
compound formed by reaction of both terminal isocyanate groups of
the diisocyanate compound of molecular formula (I) with the hydroxy
acrylate compound of molecular formula (II) where the diisocyanate
compound has undergone no reaction with the polyol of molecular
formula (II).
[0162] The di-adduct compound is formed from a reaction of the
diisocyanate compound with the hydroxy acrylate compound during the
reaction used to form the oligomer. Alternatively, the di-adduct
compound is formed independent of the reaction used to form the
oligomer and is added to the product of the reaction used to form
the polyether urethane diacrylate compound or to a purified form of
the polyether urethane diacrylate compound. The hydroxy group of
the hydroxy acrylate compound reacts with an isocyanate group of
the diisocyanate compound to provide a terminal acrylate group. The
reaction occurs at each isocyanate group of the diisocyanate
compound to form the di-adduct compound. The di-adduct compound is
present in the oligomer in an amount of at least 1.0 wt %, or at
least 1.5 wt %, or at least 2.0 wt %, or at least 2.25 wt %, or at
least 2.5 wt %, or at least 3.0 wt %, or at least 3.5 wt %, or at
least 4.0 wt %, or at least 4.5 wt %, or at least 5.0 wt %, or at
least 7.0 wt % or at least 9.0 wt %, or in the range from 1.0 wt %
to 10.0 wt %, or in the range from 2.0 wt % to 9.0 wt %, or in the
range from 2.5 wt % to 6.0 wt %, or in the range from 3.0 wt % to
8.0 wt %, or in the range from 3.0 wt % to 5.0 wt %, or in the
range from 3.0 wt % to 5.5 wt %, or in the range from 3.5 wt % to
5.0 wt %, or in the range from 3.5 wt % to 7.0 wt %. It is noted
that the concentration of di-adduct is expressed in terms of wt %
of the oligomer and not in terms of wt % in the coating
composition.
[0163] An illustrative reaction for synthesizing an oligomer in
accordance with the present disclosure includes reaction of a
diisocyanate compound (4,4'-methylene bis(cyclohexyl isocyanate,
which is also referred to herein as H12MDI) and a polyol
(polypropylene glycol with M.sub.n.about.4000 g/mol, which is also
referred to herein as PPG4000) to form a polyether urethane
diisocyanate compound with formula (VI):
H12MDI.about.PPG4000.about.H12MDI.about.PPG4000.about.H12MDI
(VI)
where ".about." denotes a urethane linkage formed by the reaction
of a terminal isocyanate group of H12MDI with a terminal alcohol
group of PPG4000; and .about.H12MDI, .about.H12DMI.about., and
.about.PPG4000 refer to residues of H12MDI and PPG4000 remaining
after the reaction; and M.sub.n refers to number average molecular
weight. The polyether urethane diisocyanate compound has a repeat
unit of the type .about.(H12MDI.about.PPG4000).about.. The
particular polyether urethane diisocyanate shown includes two
PPG4000 units. The reaction may also provide products having one
PPG4000 unit, or three or more PPG4000 units. The polyether
urethane diisocyanate and any unreacted H12MDI include terminal
isocyanate groups. In accordance with the present disclosure, a
hydroxy acrylate compound (such as 2-hydroxyethyl acrylate, which
is referred to herein as HEA) is included in the reaction to react
with terminal isocyanate groups to convert them to terminal
acrylate groups. The conversion of terminal isocyanate groups to
terminal acrylate groups effects a quenching of the isocyanate
group. The amount of HEA included in the reaction may be an amount
estimated to react stoichiometrically with the expected
concentration of unreacted isocyanate groups or an amount in excess
of the expected stoichiometric amount. Reaction of HEA with the
polyether urethane diisocyanate compound forms the polyether
urethane acrylate compound with formula (VII):
HEA.about.H12MDI.about.PPG4000.about..about.H12MDI.about.PPG4000.about.H-
12MDI (VII)
and/or the polyether urethane diacrylate compound with formula
(VIII):
HEA.about.H12MDI.about.PPG4000.about.H12MDI.about.PPG4000.about.H12MDI.a-
bout.HEA (VIII)
and reaction of HEA with unreacted H12MDI forms the di-adduct
compound with formula (IX):
HEA.about.H12MDI.about.HEA (IX)
where, as above, .about. designates a urethane linkage and
.about.HEA designates the residue of HEA remaining after reaction
to form the urethane linkage (consistent with formulas (IV) and
(V)). The combination of a polyether urethane diacrylate compound
and a di-adduct compound in the product composition constitutes an
oligomer in accordance with the present disclosure. As described
more fully hereinbelow, when one or more oligomers are used in
coating compositions, coatings having improved tear strength and
critical stress characteristics result. In particular, it is
demonstrated that oligomers having a high proportion of di-adduct
compound provide coatings with high tear strengths and/or high
critical stress values.
[0164] Although depicted for the illustrative combination of
H12MDI, HEA and PPG4000, the foregoing reaction may be generalized
to an arbitrary combination of a diisocyanate compound, a hydroxy
acrylate compound, and a polyol, where the hydroxy acrylate
compound reacts with terminal isocyanate groups to form terminal
acrylate groups and where urethane linkages form from reactions of
isocyanate groups and alcohol groups of the polyol or hydroxy
acrylate compound.
[0165] The oligomer includes a compound that is a polyether
urethane diacrylate compound with formula (X):
(hydroxy
acrylate).about.(diisocyanate.about.polyol).sub.x.about.diisocy-
anate.about.(hydroxy acrylate) (X)
and a compound that is a di-adduct compound with formula (XI):
(hydroxy acrylate).about.diisocyanate.about.(hydroxy acrylate)
(XI)
where the relative proportions of diisocyanate compound, hydroxy
acrylate compound, and polyol used in the reaction to form the
oligomer correspond to the mole numbers n, m, and p disclosed
hereinabove.
[0166] Compounds represented by molecular formulas (I) and (II)
above, for example, react to form a polyether urethane diisocyanate
compound represented by molecular formula (XII):
##STR00007##
where y is the same as y in formula (IV) and is 1, or 2, or 3 or 4
or higher; and x is determined by the number of repeat units of the
polyol (as described hereinabove).
[0167] Further reaction of the polyether urethane isocyanate of
molecular formula (VI) with the hydroxy acrylate of molecular
formula (III) provides the polyether urethane diacrylate compound
represented by molecular formula (IV) referred to hereinabove and
repeated below:
##STR00008##
where y is 1, or 2, or 3, or 4 or higher; and x is determined by
the number of repeat units of the polyol (as described
hereinabove).
[0168] In an embodiment, the reaction between the diisocyanate
compound, hydroxy acrylate compound, and polyol yields a series of
polyether urethane diacrylate compounds that differ in y such that
the average value of y over the distribution of compounds present
in the final reaction mixture is a non-integer. In an embodiment,
the average value of y in the polyether urethane diisocyanates and
polyether urethane diacrylates of molecular formulas (VI) and (IV)
corresponds to p or p-1 (where p is as defined hereinabove). In an
embodiment, the average number of occurrences of the group R.sub.1
in the polyether urethane diisocyanates and polyether urethane
diacrylates of the molecular formulas (XII) and (IV) correspond to
n (where n is as defined hereinabove).
[0169] The relative proportions of the polyether urethane
diacrylate and di-adduct compounds produced in the reaction are
controlled by varying the molar ratio of the mole numbers n, m, and
p. By way of illustration, the case where p=2.0 is considered. In
the theoretical limit of complete reaction, two equivalents p of
polyol would react with three equivalents n of a diisocyanate to
form a compound having molecular formula (VI) in which y=2. The
compound includes two terminal isocyanate groups, which can be
quenched with subsequent addition of two equivalents m of a hydroxy
acrylate compound in the theoretical limit to form the
corresponding polyether urethane diacrylate compound (IV) with y=2.
A theoretical molar ratio n:m:p=3.0:2.0:2.0 is defined for this
situation.
[0170] In the foregoing exemplary theoretical limit, a reaction of
diisocyanate, hydroxy acrylate, and polyol in the theoretical molar
ratio n:m:p=3.0:2.0:2.0 provides a polyether urethane diacrylate
compound having molecular formula (IV) in which y=2 without forming
a di-adduct compound. Variations in the mole numbers n, m, and p
provide control over the relative proportions of polyether urethane
diacrylate and di-adduct formed in the reaction. Increasing the
mole number n relative to the mole number m or the mole number p,
for example, may increase the amount of di-adduct compound formed
in the reaction. Reaction of the diisocyanate compound, the hydroxy
acrylate compound, and polyol compound in molar ratios n:m:p, where
n is in the range from 3.0 to 5.0, m is in the range within .+-.15%
of 2n-4 or within .+-.10% of 2n-4 or within .+-.5% of 2n-4, and p
is 2.0, for example, produce amounts of the di-adduct compound in
the oligomer sufficient to achieve the preferred primary coating
properties. By way of example, the embodiment in which n=4.0, m is
within .+-.15% of 2n-4, and p=2.0 means that n=4.0, m is within
.+-.15% of 4, and p=2.0, which means that that n=4.0, m is in the
range from 3.4 to 4.6, and p=2.0.
[0171] Variations in the relative proportions of di-adduct and
polyether urethane diacrylate are obtained through changes in the
mole numbers n, m, and p and through such variations, it is
possible to precisely control the Young's modulus, in situ modulus,
tear strength, critical stress, tensile toughness, and other
mechanical properties of coatings formed from coating compositions
that include the oligomer. In one embodiment, control over
properties is achievable by varying the number of units of polyol
in the polyether urethane diacrylate compound (e.g. p=2.0 vs. p=3.0
vs. p=4.0). In another embodiment, control of tear strength,
tensile toughness, and other mechanical properties is achieved by
varying the proportions polyether urethane diacrylate compound and
di-adduct compound. For a polyether urethane compound with a given
number of polyol units, oligomers having variable proportions of
di-adduct compound can be prepared. The variability in proportion
of di-adduct compound can be finely controlled to provide oligomers
based on a polyether urethane diacrylate compound with a fixed
number of polyol units that provide coatings that offer precise or
targeted values of tear strength, critical stress, tensile
toughness, or other mechanical properties.
[0172] Improved fiber primary coatings result when utilizing a
primary coating composition that incorporates an oligomer that
includes a polyether urethane acrylate compound represented by
molecular formula (IV) and a di-adduct compound represented by
molecular formula (V), where concentration of the di-adduct
compound in the oligomer is at least 1.0 wt %, or at least 1.5 wt
%, or at least 2.0 wt %, or at least 2.25 wt %, or at least 2.5 wt
%, or at least 3.0 wt %, or at least 3.5 wt %, or at least 4.0 wt
%, or at least 4.5 wt %, or at least 5.0 wt %, or at least 7.0 wt %
or at least 9.0 wt %, or in the range from 1.0 wt % to 10.0 wt %,
or in the range from 2.0 wt % to 9.0 wt %, or in the range from 3.0
wt % to 8.0 wt %, or in the range from 3.5 wt % to 7.0 wt % or in
the range from 2.5 wt % to 6.0 wt %, or in the range from 3.0 wt %
to 5.5 wt %, or in the range from 3.5 wt % to 5.0 wt %. It is noted
that the concentration of di-adduct is expressed in terms of wt %
of the oligomer and not in terms of wt % in the coating
composition. The concentration of the di-adduct compound is
increased in one embodiment by varying the molar ratio n:m:p of
diisocyanate:hydroxy acrylate:polyol. In one aspect, molar ratios
n:m:p that are rich in diisocyanate relative to polyol promote the
formation of the di-adduct compound.
[0173] In the exemplary stoichiometric ratio n:m:p=3:2:2 described
hereinabove, the reaction proceeds with p equivalents of polyol,
n=p+1 equivalents of diisocyanate, and two equivalents of hydroxy
acrylate. If the mole number n exceeds p+1, the diisocyanate
compound is present in excess relative to the amount of polyol
compound needed to form the polyether urethane acrylate of
molecular formula (IV). The presence of excess diisocyanate shifts
the distribution of reaction products toward enhanced formation of
the di-adduct compound.
[0174] To promote formation of the di-adduct compound from excess
diisocyanate compound, the amount of hydroxy acrylate can also be
increased. For each equivalent of diisocyanate above the
stoichiometric mole number n=p+1, two equivalents of hydroxy
acrylate are needed to form the di-adduct compound. In the case of
arbitrary mole number p (polyol), the stoichiometric mole numbers n
(diisocyanate) and m (hydroxy acrylate) are p+1 and 2,
respectively. As the mole number n is increased above the
stoichiometric value, the equivalents of hydroxy acrylate needed
for complete reaction of excess diisocyanate to form the di-adduct
compound may be expressed as m=2+2[n-(p+1)], where the leading term
"2" represents the equivalents of hydroxy acrylate needed to
terminate the polyether urethane acrylate compound (compound having
molecular formula (V)) and the term 2[n-(p+1)] represents the
equivalents of hydroxy acrylate needed to convert the excess
starting diisocyanate to the di-adduct compound. If the actual
value of the mole number m is less than this number of equivalents,
the available hydroxy acrylate reacts with isocyanate groups
present on the oligomer or free diisocyanate molecules to form
terminal acrylate groups. The relative kinetics of the two reaction
pathways dictates the relative amounts of polyether urethane
diacrylate and di-adduct compounds formed and the deficit in
hydroxy acrylate relative to the amount required to quench all
unreacted isocyanate groups may be controlled to further influence
the relative proportions of polyether urethane diacrylate and
di-adduct formed in the reaction.
[0175] In some embodiments, the reaction includes heating the
reaction composition formed from the diisocyanate compound, hydroxy
acrylate compound, and polyol. The heating facilitates conversion
of terminal isocyanate groups to terminal acrylate groups through a
reaction of the hydroxy acrylate compound with terminal isocyanate
groups. In different embodiments, the hydroxy acrylate compound is
present in excess in the initial reaction mixture and/or is
otherwise available or added in unreacted form to effect conversion
of terminal isocyanate groups to terminal acrylate groups. The
heating occurs at a temperature above 40.degree. C. for at least 12
hours, or at a temperature above 40.degree. C. for at least 18
hours, or at a temperature above 40.degree. C. for at least 24
hours, or at a temperature above 50.degree. C. for at least 12
hours, or at a temperature above 50.degree. C. for at least 18
hours, or at a temperature above 50.degree. C. for at least 24
hours, or at a temperature above 60.degree. C. for at least 12
hours, or at a temperature above 60.degree. C. for at least 18
hours, or at a temperature above 60.degree. C. for at least 24
hours.
[0176] In an embodiment, conversion of terminal isocyanate groups
on the polyether urethane diacrylate compound or starting
diisocyanate compound (unreacted initial amount or amount present
in excess) to terminal acrylate groups is facilitated by the
addition of a supplemental amount of hydroxy acrylate compound to
the reaction mixture. As indicated hereinabove, the amount of
hydroxy acrylate compound needed to quench (neutralize) terminal
isocyanate groups may deviate from the theoretical number of
equivalents due, for example, to incomplete reaction or a desire to
control the relative proportions of polyether urethane diacrylate
compound and di-adduct compound. As described hereinabove, once the
reaction has proceeded to completion or other endpoint, it is
preferable to quench (neutralize) residual isocyanate groups to
provide a stabilized reaction product. In an embodiment,
supplemental hydroxy acrylate is added to accomplish this
objective.
[0177] In an embodiment, the amount of supplemental hydroxy
acrylate compound is in addition to the amount included in the
initial reaction process. The presence of terminal isocyanate
groups at any stage of the reaction is monitored, for example, by
FTIR spectroscopy (e.g. using a characteristic isocyanate
stretching mode near 2265 cm.sup.-1) and supplemental hydroxy
acrylate compound is added as needed until the intensity of the
characteristic stretching mode of isocyanate groups is negligible
or below a pre-determined threshold. In an embodiment, supplemental
hydroxy acrylate compound is added beyond the amount needed to
fully convert terminal isocyanate groups to terminal acrylate
groups. In different embodiments, supplemental hydroxy acrylate
compound is included in the initial reaction mixture (as an amount
above the theoretical amount expected from the molar amounts of
diisocyanate and polyol), added as the reaction progresses, and/or
added after reaction of the diisocyanate and polyol compounds has
occurred to completion or pre-determined extent.
[0178] Amounts of hydroxy acrylate compound above the amount needed
to fully convert isocyanate groups are referred to herein as excess
amounts of hydroxy acrylate compound. When added, the excess amount
of hydroxy acrylate compound is at least 20% of the amount of
supplemental hydroxy acrylate compound needed to fully convert
terminal isocyanate groups to terminal acrylate groups, or at least
40% of the amount of supplemental hydroxy acrylate compound needed
to fully convert terminal isocyanate groups to terminal acrylate
groups, or at least 60% of the amount of supplemental hydroxy
acrylate compound needed to fully convert terminal isocyanate
groups to terminal acrylate groups, or at least 90% of the amount
of supplemental hydroxy acrylate compound needed to fully convert
terminal isocyanate groups to terminal acrylate groups.
[0179] In an embodiment, the amount of supplemental hydroxy
acrylate compound may be sufficient to completely or nearly
completely quench residual isocyanate groups present in the
oligomer formed in the reaction. Quenching of isocyanate groups is
desirable because isocyanate groups are relatively unstable and
often undergo reaction over time. Such reaction alters the
characteristics of the reaction composition or oligomer and may
lead to inconsistencies in coatings formed therefrom. Reaction
compositions and products formed from the starting diisocyanate and
polyol compounds that are free of residual isocyanate groups are
expected to have greater stability and predictability of
characteristics.
[0180] The oligomer of the primary coating composition includes a
polyether urethane diacrylate compound and di-adduct compound as
described hereinabove. In some embodiments, the oligomer includes
two or more polyether urethane diacrylate compounds and/or two or
more di-adduct compounds. The oligomer content of the primary
coating composition includes the combined amounts of the one or
more polyether urethane diacrylate compound(s) and one or more
di-adduct compound(s) and is greater than 20 wt %, or greater than
30 wt %, or greater than 40 wt %, or in the range from 20 wt % to
80 wt %, or in the range from 30 wt % to 70 wt %, or in the range
from 40 wt % to 60 wt %, where the concentration of di-adduct
compound within the oligomer content is as described above.
[0181] The curable primary coating composition further includes one
or more monomers. The one or more monomers is/are selected to be
compatible with the oligomer, to control the viscosity of the
primary coating composition to facilitate processing, and/or to
influence the physical or chemical properties of the coating formed
as the cured product of the primary coating composition. The
monomers include radiation-curable monomers such as
ethylenically-unsaturated compounds, ethoxylated acrylates,
ethoxylated alkylphenol monoacrylates, propylene oxide acrylates,
n-propylene oxide acrylates, isopropylene oxide acrylates,
monofunctional acrylates, monofunctional aliphatic epoxy acrylates,
multifunctional acrylates, multifunctional aliphatic epoxy
acrylates, and combinations thereof.
[0182] Representative radiation-curable ethylenically unsaturated
monomers include alkoxylated monomers with one or more acrylate or
methacrylate groups. An alkoxylated monomer is one that includes
one or more alkoxylene groups, where an alkoxylene group has the
form --O--R-- and R is a linear or branched alkylene group.
Examples of alkoxylene groups include ethoxylene
(--O--CH.sub.2--CH.sub.2--), n-propoxylene
(--O--CH.sub.2--CH.sub.2--CH.sub.2--), isopropoxylene
(--O--CH.sub.2--CH(CH.sub.3)--, or --O--CH(CH.sub.3)--CH.sub.2--),
etc. As used herein, the degree of alkoxylation refers to the
number of alkoxylene groups in the monomer. In one embodiment, the
alkoxylene groups are bonded consecutively in the monomer.
[0183] In some embodiments, the primary coating composition
includes an alkoxylated monomer of the form
R.sub.4-R.sub.5--O--(CH(CH.sub.3)CH.sub.2--O).sub.q--C(O)CH.dbd.CH.sub.2,
where R.sub.4 and R.sub.5 are aliphatic, aromatic, or a mixture of
both, and q=1 to 10, or
R.sub.4--O--(CH(CH.sub.3)CH.sub.2--O).sub.q--C(O)CH.dbd.CH.sub.2,
where C(O) is a carbonyl group, R.sub.1 is aliphatic or aromatic,
and q=1 to 10.
[0184] Representative examples of monomers include ethylenically
unsaturated monomers such as lauryl acrylate (e.g., SR335 available
from Sartomer Company, Inc., AGEFLEX FA12 available from BASF, and
PHOTOMER 4812 available from IGM Resins), ethoxylated nonylphenol
acrylate (e.g., SR504 available from Sartomer Company, Inc. and
PHOTOMER 4066 available from IGM Resins), caprolactone acrylate
(e.g., SR495 available from Sartomer Company, Inc., and TONE M-100
available from Dow Chemical), phenoxyethyl acrylate (e.g., SR339
available from Sartomer Company, Inc., AGEFLEX PEA available from
BASF, and PHOTOMER 4035 available from IGM Resins), isooctyl
acrylate (e.g., SR440 available from Sartomer Company, Inc. and
AGEFLEX FA8 available from BASF), tridecyl acrylate (e.g., SR489
available from Sartomer Company, Inc.), isobornyl acrylate (e.g.,
SR506 available from Sartomer Company, Inc. and AGEFLEX IBOA
available from CPS Chemical Co.), tetrahydrofurfuryl acrylate
(e.g., SR285 available from Sartomer Company, Inc.), stearyl
acrylate (e.g., SR257 available from Sartomer Company, Inc.),
isodecyl acrylate (e.g., SR395 available from Sartomer Company,
Inc. and AGEFLEX FA10 available from BASF), 2-(2-ethoxyethoxy)ethyl
acrylate (e.g., SR256 available from Sartomer Company, Inc.), epoxy
acrylate (e.g., CN120, available from Sartomer Company, and EBECRYL
3201 and 3604, available from Cytec Industries Inc.),
lauryloxyglycidyl acrylate (e.g., CN130 available from Sartomer
Company) and phenoxyglycidyl acrylate (e.g., CN131 available from
Sartomer Company) and combinations thereof.
[0185] In some embodiments, the monomer component of the primary
coating composition includes a multifunctional (meth)acrylate.
Multifunctional ethylenically unsaturated monomers include
multifunctional acrylate monomers and multifunctional methacrylate
monomers. Multifunctional acrylates are acrylates having two or
more polymerizable acrylate moieties per molecule, or three or more
polymerizable acrylate moieties per molecule. Examples of
multifunctional (meth)acrylates include dipentaerythritol
monohydroxy pentaacrylate (e.g., PHOTOMER 4399 available from IGM
Resins); methylolpropane polyacrylates with and without
alkoxylation such as trimethylolpropane triacrylate,
ditrimethylolpropane tetraacrylate (e.g., PHOTOMER 4355, IGM
Resins); alkoxylated glyceryl triacrylates such as propoxylated
glyceryl triacrylate with propoxylation being 3 or greater (e.g.,
PHOTOMER 4096, IGM Resins); and erythritol polyacrylates with and
without alkoxylation, such as pentaerythritol tetraacrylate (e.g.,
SR295, available from Sartomer Company, Inc. (Westchester, Pa.)),
ethoxylated pentaerythritol tetraacrylate (e.g., SR494, Sartomer
Company, Inc.), dipentaerythritol pentaacrylate (e.g., PHOTOMER
4399, IGM Resins, and SR399, Sartomer Company, Inc.),
tripropyleneglycol diacrylate, propoxylated hexanediol diacrylate,
tetrapropyleneglycol diacrylate, pentapropyleneglycol diacrylate,
methacrylate analogs of the foregoing, and combinations
thereof.
[0186] In some embodiments, the primary coating composition
includes an N-vinyl amide monomer such as an N-vinyl lactam, or
N-vinyl pyrrolidinone, or N-vinyl caprolactam, where the N-vinyl
amide monomer is present in the coating composition at a
concentration greater than 1.0 wt %, or greater than 2.0 wt %, or
greater than 3.0 wt %, or in the range from 1.0 wt % to 15.0 wt %,
or in the range from 2.0 wt % to 10.0 wt %, or in the range from
3.0 wt % to 8.0 wt %.
[0187] In an embodiment, the primary coating composition includes
one or more monofunctional acrylate or methacrylate monomers in an
amount from 15 wt % to 90 wt %, or from 30 wt % to 75 wt %, or from
40 wt % to 65 wt %. In another embodiment, the primary coating
composition may include one or more monofunctional aliphatic epoxy
acrylate or methacrylate monomers in an amount from 5 wt % to 40 wt
%, or from 10 wt % to 30 wt %.
[0188] In an embodiment, the monomer component of the primary
coating composition includes a hydroxyfunctional monomer. A
hydroxyfunctional monomer is a monomer that has a pendant hydroxy
moiety in addition to other reactive functionality such as
(meth)acrylate. Examples of hydroxyfunctional monomers including
pendant hydroxyl groups include caprolactone acrylate (available
from Dow Chemical as TONE M-100); poly(alkylene glycol)
mono(meth)acrylates, such as poly(ethylene glycol) monoacrylate,
poly(propylene glycol) monoacrylate, and poly(tetramethylene
glycol) monoacrylate (each available from Monomer, Polymer &
Dajac Labs); 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl
(meth)acrylate, and 4-hydroxybutyl (meth)acrylate (each available
from Aldrich).
[0189] In an embodiment, the hydroxyfunctional monomer is present
in an amount sufficient to improve adhesion of the primary coating
to the optical fiber. The hydroxyfunctional monomer is present in
the coating composition in an amount between about 0.1 wt % and
about 25 wt %, or in an amount between about 5 wt % and about 8 wt
%. The use of the hydroxyfunctional monomer may decrease the amount
of adhesion promoter necessary for adequate adhesion of the primary
coating to the optical fiber. The use of the hydroxyfunctional
monomer may also tend to increase the hydrophilicity of the
coating. Hydroxyfunctional monomers are described in more detail in
U.S. Pat. No. 6,563,996, the disclosure of which is hereby
incorporated by reference in its entirety.
[0190] In different embodiments, the total monomer content of the
primary coating composition is between about 15 wt % and about 90
wt %, or between about 30 wt % and about 75 wt %, or between about
40 wt % and about 65 wt %.
[0191] In addition to a curable monomer and a curable oligomer, the
curable primary coating composition also includes a polymerization
initiator. The polymerization initiator facilitates initiation of
the polymerization process associated with the curing of the
coating composition to form the coating. Polymerization initiators
include thermal initiators, chemical initiators, electron beam
initiators, and photoinitiators. Photoinitiators include ketonic
photoinitiators and/or phosphine oxide photoinitiators. When used
in the curing of the coating composition, the photoinitiator is
present in an amount sufficient to enable rapid radiation
curing.
[0192] Representative photoinitiators include
1-hydroxycyclohexylphenyl ketone (e.g., IRGACURE 184 available from
BASF)); bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine
oxide (e.g., commercial blends IRGACURE 1800, 1850, and 1700
available from BASF); 2,2-dimethoxy-2-phenylacetophenone (e.g.,
IRGACURE 651, available from BASF);
bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819);
(2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (LUCIRIN TPO,
available from BASF (Munich, Germany));
ethoxy(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (LUCIRIN TPO-L
from BASF); and combinations thereof.
[0193] The coating composition includes a single photoinitiator or
a combination of two or more photoinitiators. The total
photoinitiator content of the coating composition is up to about 10
wt %, or between about 0.5 wt % and about 6 wt %.
[0194] The curable primary coating composition optionally includes
one or more additives. Additives include an adhesion promoter, a
strength additive, an antioxidant, a catalyst, a stabilizer, an
optical brightener, a property-enhancing additive, an amine
synergist, a wax, a lubricant, and/or a slip agent. Some additives
operate to control the polymerization process, thereby affecting
the physical properties (e.g., modulus, glass transition
temperature) of the polymerization product formed from the coating
composition. Other additives affect the integrity of the cured
product of the primary coating composition (e.g., protect against
de-polymerization or oxidative degradation).
[0195] An adhesion promoter is a compound that facilitates adhesion
of the primary coating and/or primary composition to glass (e.g.
the cladding portion of a glass fiber). Suitable adhesion promoters
include alkoxysilanes, mercapto-functional silanes,
organotitanates, and zirconates. Representative adhesion promoters
include mercaptoalkyl silanes or mercaptoalkoxy silanes such as
3-mercaptopropyl-trialkoxysilane (e.g.,
3-mercaptopropyl-trimethoxysilane, available from Gelest
(Tullytown, Pa.)); bis(trialkoxysilyl-ethyl)benzene;
acryloxypropyltrialkoxysilane (e.g.,
(3-acryloxypropyl)-trimethoxysilane, available from Gelest),
methacryloxypropyltrialkoxysilane, vinyltrialkoxysilane,
bis(trialkoxysilylethyl)hexane, allyltrialkoxysilane,
styrylethyltrialkoxysilane, and bis(trimethoxysilylethyl)benzene
(available from United Chemical Technologies (Bristol, Pa.)); see
U.S. Pat. No. 6,316,516, the disclosure of which is hereby
incorporated by reference in its entirety herein.
[0196] The adhesion promoter is present in the primary coating
composition in an amount between 0.02 wt % and 10.0 wt %, or
between 0.05 wt % and 4.0 wt %, or between 0.1 wt % and 4.0 wt %,
or between 0.1 wt % and 3.0 wt %, or between 0.1 wt % and 2.0 wt %,
or between 0.1 wt % and 1.0 wt %, or between 0.5 wt % and 4.0 wt %,
or between 0.5 wt % and 3.0 wt %, or between 0.5 wt % and 2.0 wt %,
or between 0.5 wt % and 1.0 wt %.
[0197] A representative antioxidant is thiodiethylene
bis[3-(3,5-di-tert-butyl)-4-hydroxy-phenyl) propionate] (e.g.,
IRGANOX 1035, available from BASF). In some aspects, an antioxidant
is present in the coating composition in an amount greater than
0.25 wt %, or greater than 0.50 wt %, or greater than 0.75 wt %, or
greater than 1.0 wt %, or an amount in the range from 0.25 wt % to
3.0 wt %, or an amount in the range from 0.50 wt % to 2.0 wt %, or
an amount in the range from 0.75 wt % to 1.5 wt %.
[0198] Representative optical brighteners include TINOPAL OB
(available from BASF); Blankophor KLA (available from Bayer);
bisbenzoxazole compounds; phenylcoumarin compounds; and
bis(styryl)biphenyl compounds. In an embodiment, the optical
brightener is present in the coating composition at a concentration
of 0.005 wt % to 0.3 wt %.
[0199] Representative amine synergists include triethanolamine;
1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine, and
methyldiethanolamine. In an embodiment, an amine synergist is
present at a concentration of 0.02 wt % to 0.5 wt %.
[0200] Primary Coating-Properties. Relevant properties of the
primary coating include radius, thickness, Young's modulus, and in
situ modulus.
[0201] The radius r.sub.5 of the primary coating is less than or
equal to 85.0 microns, or less than or equal to 80.0 microns, or
less than or equal to 75.0 microns, or less than or equal to 70.0
microns.
[0202] To facilitate decreases in the diameter of the optical
fiber, it is preferable to minimize the thickness r.sub.5-r.sub.4
of the primary coating. The thickness r.sub.5-r.sub.4 of the
primary coating is less than or equal to 25.0 microns, or less than
or equal to 20.0 microns, or less than or equal to 15.0 microns, or
less than or equal to 10.0 microns, or in the range from 5.0
microns to 25.0 microns, or in the range from 8.0 microns to 20.0
microns, or in the range from 10.0 microns to 17.0 microns.
[0203] To facilitate effective buffering of stress and protection
of the glass fiber, it is preferable for the primary coating to
have a low Young's modulus and/or a low in situ modulus. The
Young's modulus of the primary coating is less than or equal to 0.7
MPa, or less than or equal to 0.6 MPa, or less than or equal to 0.5
MPa, or less than or equal to 0.4 MPa, or in the range from 0.2 MPa
to 0.7 MPa, or in the range from 0.3 MPa to 0.6 MPa. The in situ
modulus of the primary coating is less than or equal to 0.25 MPa,
or less than or equal to 0.20 MPa, or less than or equal to 0.15
MPa, or less than or equal to 0.10 MPa, or in the range from 0.05
MPa to 0.25 MPa, or in the range from 0.10 MPa to 0.20 MPa.
[0204] Secondary Coating--Compositions. The secondary coating is a
cured product of a curable secondary coating composition that
includes a monomer, a photoinitiator, an optional oligomer, and an
optional additive. The present disclosure describes optional
oligomers for the radiation-curable secondary coating compositions,
radiation-curable secondary coating compositions, cured products of
the radiation-curable secondary coating compositions, optical
fibers coated with a radiation-curable secondary coating
composition, and optical fibers coated with the cured product of a
radiation-curable secondary coating composition.
[0205] The secondary coating is formed as the cured product of a
radiation-curable secondary coating composition that includes a
monomer component with one or more monomers. The monomers
preferably include ethylenically unsaturated compounds. The one or
more monomers may be present in an amount of 50 wt % or greater, or
in an amount from about 60 wt % to about 99 wt %, or in an amount
from about 75 wt % to about 99 wt %, or in an amount from about 80
wt % to about 99 wt % or in an amount from about 85 wt % to about
99 wt %. In one embodiment, the secondary coating is the
radiation-cured product of a secondary coating composition that
contains urethane acrylate monomers.
[0206] The monomers include functional groups that are
polymerizable groups and/or groups that facilitate or enable
crosslinking. The monomers are monofunctional monomers or
multifunctional monomers. In combinations of two or more monomers,
the constituent monomers are monofunctional monomers,
multifunctional monomers, or a combination of monofunctional
monomers and multifunctional monomers. In one embodiment, the
monomer component of the curable secondary coating composition
includes ethylenically unsaturated monomers. Suitable functional
groups for ethylenically unsaturated monomers include, without
limitation, (meth)acrylates, acrylamides, N-vinyl amides, styrenes,
vinyl ethers, vinyl esters, acid esters, and combinations
thereof.
[0207] In one embodiment, the monomer component of the curable
secondary coating composition includes ethylenically unsaturated
monomers. The monomers include functional groups that are
polymerizable groups and/or groups that facilitate or enable
crosslinking. The monomers are monofunctional monomers or
multifunctional monomers. In combinations of two or more monomers,
the constituent monomers are monofunctional monomers,
multifunctional monomers, or a combination of monofunctional
monomers and multifunctional monomers. Suitable functional groups
for ethylenically unsaturated monomers include, without limitation,
(meth)acrylates, acrylamides, N-vinyl amides, styrenes, vinyl
ethers, vinyl esters, acid esters, and combinations thereof.
[0208] Exemplary monofunctional ethylenically unsaturated monomers
for the curable secondary coating composition include, without
limitation, hydroxyalkyl acrylates such as 2-hydroxyethyl-acrylate,
2-hydroxypropyl-acrylate, and 2-hydroxybutyl-acrylate; long- and
short-chain alkyl acrylates such as methyl acrylate, ethyl
acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, amyl
acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate,
isoamyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate,
isooctyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl
acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate,
lauryl acrylate, octadecyl acrylate, and stearyl acrylate;
aminoalkyl acrylates such as dimethylaminoethyl acrylate,
diethylaminoethyl acrylate, and 7-amino-3,7-dimethyloctyl acrylate;
alkoxyalkyl acrylates such as butoxyethyl acrylate, phenoxyethyl
acrylate (e.g., SR339, Sartomer Company, Inc.), and
ethoxyethoxyethyl acrylate; single and multi-ring cyclic aromatic
or non-aromatic acrylates such as cyclohexyl acrylate, benzyl
acrylate, dicyclopentadiene acrylate, dicyclopentanyl acrylate,
tricyclodecanyl acrylate, bomyl acrylate, isobornyl acrylate (e.g.,
SR423, Sartomer Company, Inc.), tetrahydrofiurfuryl acrylate (e.g.,
SR285, Sartomer Company, Inc.), caprolactone acrylate (e.g., SR495,
Sartomer Company, Inc.), and acryloylmorpholine; alcohol-based
acrylates such as polyethylene glycol monoacrylate, polypropylene
glycol monoacrylate, methoxyethylene glycol acrylate,
methoxypolypropylene glycol acrylate, methoxypolyethylene glycol
acrylate, ethoxydiethylene glycol acrylate, and various alkoxylated
alkylphenol acrylates such as ethoxylated(4) nonylphenol acrylate
(e.g., Photomer 4066, IGM Resins); acrylamides such as diacetone
acrylamide, isobutoxymethyl acrylamide, N,N'-dimethyl-aminopropyl
acrylamide, N,N-dimethyl acrylamide, N,N diethyl acrylamide, and
t-octyl acrylamide; vinylic compounds such as N-vinylpyrrolidone
and N-vinylcaprolactam; and acid esters such as maleic acid ester
and fumaric acid ester. With respect to the long and short chain
alkyl acrylates listed above, a short chain alkyl acrylate is an
alkyl group with 6 or less carbons and a long chain alkyl acrylate
is an alkyl group with 7 or more carbons.
[0209] Representative radiation-curable ethylenically unsaturated
monomers included alkoxylated monomers with one or more acrylate or
methacrylate groups. An alkoxylated monomer is one that includes
one or more alkoxylene groups, where an alkoxylene group has the
form --O--R-- and R is a linear or branched hydrocarbon. Examples
of alkoxylene groups include ethoxylene
(--O--CH.sub.2--CH.sub.2--), n-propoxylene
(--O--CH.sub.2--CH.sub.2--CH.sub.2--), isopropoxylene
(--O--CH.sub.2--CH(CH.sub.3)--), etc. As used herein, the degree of
alkoxylation refers to the number of alkoxylene groups in the
monomer. In one embodiment, the alkoxylene groups are bonded
consecutively in the monomer.
[0210] As used herein, degree of alkoxylation refers to the number
of alkoxylene groups divided by the number of acrylate and
methacrylate groups in a molecule of the monomer. For
monofunctional alkoxylated monomers, the degree of alkoxylation
corresponds to the number of alkoxylene groups in a molecule of the
monomer. In a preferred embodiment, the alkoxylene groups of a
monofunctional alkoxylated monomer are bonded consecutively. For a
difunctional alkoxylated monomer, the degree of alkoxylation
corresponds to one half of the number of alkoxylene groups in a
molecule of the monomer. In a preferred embodiment, the alkoxylene
groups in a difunctional alkoxylated monomer are bonded
consecutively in each of two groups where the two groups are
separated by a chemical linkage and each group includes half or
approximately half of the number of alkoxylene groups in the
molecule. For a trifunctional alkoxylated monomer, the degree of
alkoxylation corresponds to one third of the number of alkoxylene
groups in a molecule of the monomer. In a preferred embodiment, the
alkoxylene groups in a trifunctional alkoxylated monomer are bonded
consecutively in three groups, where the three groups are separated
by chemical linkages and each group includes a third or
approximately a third of the number of alkoxylene groups in the
molecule.
[0211] Representative multifunctional ethylenically unsaturated
monomers for the curable secondary coating composition include,
without limitation, alkoxylated bisphenol-A diacrylates, such as
ethoxylated bisphenol-A diacrylate, and alkoxylated
trimethylolpropane triacrylates, such as ethoxylated
trimethylolpropane triacrylate, with the degree of alkoxylation
being 2 or greater, or 4 or greater, or 6 or greater, or less than
16 or less than 12, or less than 8, or less than 5, or in the range
from 2 to 16, or in the range from 2 to 12, or in the range from 2
to 8, or in the range from 2 to 4, or in the range from 3 to 12, or
in the range from 3 to 8, or in the range from 3 to 5, or in the
range from 4 to 12, or in the range from 4 to 10, or in the range
from 4 to 8.
[0212] Multifunctional ethylenically unsaturated monomers for the
curable secondary coating composition include, without limitation,
alkoxylated bisphenol A diacrylates, such as ethoxylated bisphenol
A diacrylate, with the degree of alkoxylation being 2 or greater.
The monomer component of the secondary coating composition may
include ethoxylated bisphenol A diacrylate with a degree of
ethoxylation ranging from 2 to about 30 (e.g. SR349, SR601, and
SR602 available from Sartomer Company, Inc. West Chester, Pa. and
Photomer 4025 and Photomer 4028, available from IGM Resins), or
propoxylated bisphenol A diacrylate with the degree of
propoxylation being 2 or greater; for example, ranging from 2 to
about 30; methylolpropane polyacrylates with and without
alkoxylation such as ethoxylated trimethylolpropane triacrylate
with the degree of ethoxylation being 3 or greater; for example,
ranging from 3 to about 30 (e.g., Photomer 4149, IGM Resins, and
SR499, Sartomer Company, Inc.); propoxylated-trimethylolpropane
triacrylate with the degree of propoxylation being 3 or greater;
for example, ranging from 3 to 30 (e.g., Photomer 4072, IGM Resins
and SR492, Sartomer); ditrimethylolpropane tetraacrylate (e.g.,
Photomer 4355, IGM Resins); alkoxylated glyceryl triacrylates such
as propoxylated glyceryl triacrylate with the degree of
propoxylation being 3 or greater (e.g., Photomer 4096, IGM Resins
and SR9020, Sartomer); erythritol polyacrylates with and without
alkoxylation, such as pentaerythritol tetraacrylate (e.g., SR295,
available from Sartomer Company, Inc. (West Chester, Pa.)),
ethoxylated pentaerythritol tetraacrylate (e.g., SR494, Sartomer
Company, Inc.), and dipentaerythritol pentaacrylate (e.g., Photomer
4399, IGM Resins, and SR399, Sartomer Company, Inc.); isocyanurate
polyacrylates formed by reacting an appropriate functional
isocyanurate with an acrylic acid or acryloyl chloride, such as
tris-(2-hydroxyethyl) isocyanurate triacrylate (e.g., SR368,
Sartomer Company, Inc.) and tris-(2-hydroxyethyl) isocyanurate
diacrylate; alcohol polyacrylates with and without alkoxylation
such as tricyclodecane dimethanol diacrylate (e.g., CD406, Sartomer
Company, Inc.) and ethoxylated polyethylene glycol diacrylate with
the degree of ethoxylation being 2 or greater; for example, ranging
from about 2 to 30; epoxy acrylates formed by adding acrylate to
bisphenol A diglycidylether and the like (e.g., Photomer 3016, IGM
Resins); and single and multi-ring cyclic aromatic or non-aromatic
polyacrylates such as dicyclopentadiene diacrylate and
dicyclopentane diacrylate.
[0213] Multifunctional ethylenically unsaturated monomers of the
curable secondary coating composition include ethoxylated
bisphenol-A diacrylate with a degree of ethoxylation ranging from 2
to 16 (e.g. SR349, SR601, and SR602 available from Sartomer
Company, Inc. West Chester, Pa. and Photomer 4028, available from
IGM Resins), or propoxylated bisphenol-A diacrylate with the degree
of propoxylation being 2 or greater; for example, ranging from 2 to
16; methylolpropane polyacrylates with and without alkoxylation
such as alkoxylated trimethylolpropane triacrylate or ethoxylated
trimethylolpropane triacrylate with the degree of alkoxylation or
ethoxylation being 2 or greater; for example, ranging from 2 to 16
or from 3 to 10 (e.g., Photomer 4149, IGM Resins, and SR499,
Sartomer Company, Inc.); propoxylated-trimethylolpropane
triacrylate with the degree of propoxylation being 2 or greater;
for example, ranging from 2 to 16 (e.g., Photomer 4072, IGM Resins
and SR492, Sartomer); ditrimethylolpropane tetraacrylate (e.g.,
Photomer 4355, IGM Resins); alkoxylated glyceryl triacrylates such
as propoxylated glyceryl triacrylate with the degree of
propoxylation being 2 or greater; for example, ranging from 2 to 16
(e.g., Photomer 4096, IGM Resins and SR9020, Sartomer); erythritol
polyacrylates with and without alkoxylation, such as
pentaerythritol tetraacrylate (e.g., SR295, available from Sartomer
Company, Inc. (West Chester, Pa.)), ethoxylated pentaerythritol
tetraacrylate (e.g., SR494, Sartomer Company, Inc.), and
dipentaerythritol pentaacrylate (e.g., Photomer 4399, IGM Resins,
and SR399, Sartomer Company, Inc.); isocyanurate polyacrylates
formed by reacting an appropriate functional isocyanurate with an
acrylic acid or acryloyl chloride, such as tris-(2-hydroxyethyl)
isocyanurate triacrylate (e.g., SR368, Sartomer Company, Inc.) and
tris-(2-hydroxyethyl) isocyanurate diacrylate; alcohol
polyacrylates with and without alkoxylation such as tricyclodecane
dimethanol diacrylate (e.g., CD406, Sartomer Company, Inc.) and
ethoxylated polyethylene glycol diacrylate with the degree of
ethoxylation being 2 or greater; for example, ranging from 2 to 16;
epoxy acrylates formed by adding acrylate to bisphenol-A
diglycidylether and the like (e.g., Photomer 3016, IGM Resins); and
single and multi-ring cyclic aromatic or non-aromatic polyacrylates
such as dicyclopentadiene diacrylate and dicyclopentane
diacrylate.
[0214] In some embodiments, the curable secondary coating
composition includes a multifunctional monomer with three or more
curable functional groups in an amount greater than 2.0 wt %, or
greater than 5.0 wt %, or greater than 7.5 wt %, or greater than 10
wt %, or greater than 15 wt %, or greater than 20 wt %, or in the
range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20
wt %, or in the range from 8.0 wt % to 15 wt %. In a preferred
embodiment, each of the three or more curable functional groups is
an acrylate group.
[0215] In some embodiments, the curable secondary coating
composition includes a trifunctional monomer in an amount greater
than 2.0 wt %, or greater than 5.0 wt %, or greater than 7.5 wt %,
or greater than 10 wt %, or greater than 15 wt %, or greater than
20 wt %, or in the range from 2.0 wt % to 25 wt %, or in the range
from 5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %.
In a preferred embodiment, the trifunctional monomer is a
triacrylate monomer.
[0216] In some embodiments, the curable secondary coating
composition includes a difunctional monomer in an amount greater
than 55 wt %, or greater than 60 wt %, or greater than 65 wt %, or
greater than 70 wt %, or in the range from 55 wt % to 80 wt %, or
in the range from 60 wt % to 75 wt %, and further includes a
trifunctional monomer in an amount in the range from 2.0 wt % to 25
wt %, or in the range from 5.0 wt % to 20 wt %, or in the range
from 8.0 wt % to 15 wt %. In a preferred embodiment, the
difunctional monomer is a diacrylate monomer and the trifunctional
monomer is a triacrylate monomer. Preferred diacrylate monomers
include alkoxylated bisphenol-A diacrylates. Preferred triacrylate
monomers include alkoxylated trimethylolpropane triacrylates and
isocyanurate triacrylates. Preferably the curable secondary coating
composition lacks an alkoxylated bisphenol-A diacrylate having a
degree of alkoxylation greater than 17, or greater than 20, or
greater than 25, or in the range from 15 to 40, or in the range
from 20 to 35.
[0217] In some embodiments, the curable secondary coating
composition lacks a monofunctional monomer and includes a
difunctional monomer in an amount greater than 55 wt %, or greater
than 60 wt %, or greater than 65 wt %, or greater than 70 wt %, or
in the range from 55 wt % to 80 wt %, or in the range from 60 wt %
to 75 wt %, and further includes a trifunctional monomer in an
amount in the range from 2.0 wt % to 25 wt %, or in the range from
5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %. In a
preferred embodiment, the difunctional monomer is a diacrylate
monomer and the trifunctional monomer is a triacrylate monomer.
Preferred diacrylate monomers include alkoxylated bisphenol-A
diacrylates. Preferred triacrylate monomers include alkoxylated
trimethylolpropane triacrylates and isocyanurate triacrylates.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0218] In some embodiments, the curable secondary coating
composition includes two or more difunctional monomers in a
combined amount greater than 70 wt %, or greater than 75 wt %, or
greater than 80 wt %, or greater than 85 wt %, or in the range from
70 wt % to 95 wt %, or in the range from 75 wt % to 90 wt %, and
further includes a trifunctional monomer in an amount in the range
from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20 wt %,
or in the range from 8.0 wt % to 15 wt %. In a preferred
embodiment, the difunctional monomer is a diacrylate monomer and
the trifunctional monomer is a triacrylate monomer. Preferred
diacrylate monomers include alkoxylated bisphenol-A diacrylates.
Preferred triacrylate monomers include alkoxylated
trimethylolpropane triacrylates and isocyanurate triacrylates.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0219] In some embodiments, the curable secondary coating
composition lacks a monofunctional monomer and includes two or more
difunctional monomers in a combined amount greater than 70 wt %, or
greater than 75 wt %, or greater than 80 wt %, or greater than 85
wt %, or in the range from 70 wt % to 95 wt %, or in the range from
75 wt % to 90 wt %, and further includes a trifunctional monomer in
an amount in the range from 2.0 wt % to 25 wt %, or in the range
from 5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %.
In a preferred embodiment, the difunctional monomer is a diacrylate
monomer and the trifunctional monomer is a triacrylate monomer.
Preferred diacrylate monomers include alkoxylated bisphenol-A
diacrylates. Preferred triacrylate monomers include alkoxylated
trimethylolpropane triacrylates and isocyanurate triacrylates.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0220] In some embodiments, the curable secondary coating
composition includes two or more difunctional monomers in a
combined amount greater than 70 wt %, or greater than 75 wt %, or
greater than 80 wt %, or greater than 85 wt %, or in the range from
70 wt % to 95 wt %, or in the range from 75 wt % to 90 wt %, and
further includes two or more trifunctional monomers in a combined
amount in the range from 2.0 wt % to 25 wt %, or in the range from
5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %. In a
preferred embodiment, each of the two or more difunctional monomers
is a diacrylate monomer and each of the two or more trifunctional
monomers is a triacrylate monomer. Preferred diacrylate monomers
include alkoxylated bisphenol-A diacrylates. Preferred triacrylate
monomers include alkoxylated trimethylolpropane triacrylates and
isocyanurate triacrylates. Preferably the curable secondary coating
composition lacks an alkoxylated bisphenol-A diacrylate having a
degree of alkoxylation greater than 17, or greater than 20, or
greater than 25, or in the range from 15 to 40, or in the range
from 20 to 35.
[0221] In some embodiments, the curable secondary coating
composition lacks a monofunctional monomer and includes two or more
difunctional monomers in a combined amount greater than 70 wt %, or
greater than 75 wt %, or greater than 80 wt %, or greater than 85
wt %, or in the range from 70 wt % to 95 wt %, or in the range from
75 wt % to 90 wt %, and further includes two or more trifunctional
monomers in a combined amount in the range from 2.0 wt % to 25 wt
%, or in the range from 5.0 wt % to 20 wt %, or in the range from
8.0 wt % to 15 wt %. In a preferred embodiment, the each of the
difunctional monomers is a diacrylate monomer and each of the
trifunctional monomers is a triacrylate monomer. Preferred
diacrylate monomers include alkoxylated bisphenol-A diacrylates.
Preferred triacrylate monomers include alkoxylated
trimethylolpropane triacrylates and isocyanurate triacrylates.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0222] A preferred difunctional monomer is an alkoxylated
bisphenol-A diacrylate. Alkoxylated bisphenol-A diacrylate has the
general formula (XIII):
##STR00009##
where R.sub.1 and R.sub.2 are alkylene groups, R.sub.1--O and
R.sub.2--O are alkoxylene groups, and R.sub.3 is H. Any two of the
groups R.sub.1, R.sub.2, and R.sub.3 are the same or different. In
one embodiment, the groups R.sub.1 and R.sub.2 are the same. The
number of carbons in each of the groups R.sub.1 and R.sub.2 is in
the range from 1 to 8, or in the range from 2 to 6, or in the range
from 2 to 4. The degree of alkoxylation is 1/2(x+y). The values of
x and yare the same or different. In one embodiment, x and yare the
same.
[0223] A preferred trifunctional monomer is an alkoxylated
trimethylolpropane triacrylate. Alkoxylated trimethylolpropane
triacrylate has the general formula (XIV):
##STR00010##
where R.sub.1 and R.sub.2 are alkylene groups, O--R.sub.1,
O--R.sub.2, O--R.sub.3 are alkoxylene groups. Any two of the groups
R.sub.1, R.sub.2, and R.sub.3 are the same or different. In one
embodiment, the groups R.sub.1, R.sub.2, and R.sub.3 are the same.
The number of carbons in the each of the groups R.sub.1, R.sub.2
and R.sub.3 is in the range from 1 to 8, or in the range from 2 to
6, or in the range from 2 to 4. The degree of alkoxylation is
1/3(x+y+z). The values of any two of x, y and z are the same or
different. In one embodiment, x, y, and z are the same.
[0224] Another preferred trifunctional monomer is a
tris[(acryloyloxy)alkyl]isocyanurate.
Tris[(acryloyloxy)alkyl]isocyanurates are also referred to as
tris[n-hydroxyalkyl) isocyanurate triacrylates. A representative
tris[(acryloyloxy)alkyl] isocyanurate is tris[2-hydroxyethyl)
isocyanurate triacrylate, which has the general formula (XV):
##STR00011##
In formula (III), an ethylene linkage (--CH.sub.2--CH.sub.2--)
bonds each acryloyloxy group to a nitrogen of the isocyanurate
ring. In other embodiments of tris[(acryloyloxy)alkyl]
isocyanurates, alkylene linkages other than ethylene bond the
acryloyloxy groups to nitrogen atoms of the isocyanurate ring. The
alkylene linkages for any two of the three alkylene linkages are
the same or different. In one embodiment, the three alkylene
linkages are the same. The number of carbons in each of the
alkylene linkages is in the range from 1 to 8, or in the range from
2 to 6, or in the range from 2 to 4.
[0225] In one embodiment, the curable secondary composition
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an alkoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0226] In one embodiment, the curable secondary composition
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an ethoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0227] In one embodiment, the curable secondary composition
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an alkoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0228] In one embodiment, the curable secondary composition
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an ethoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0229] In one embodiment, the curable secondary composition
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris[(acryloyloxy)alkyl] isocyanurate monomer in an amount in the
range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20
wt %, or in the range from 8.0 wt % to 15 wt %. Preferably the
curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0230] In one embodiment, the curable secondary composition
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris[(acryloyloxy)alkyl] isocyanurate monomer in an amount in the
range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20
wt %, or in the range from 8.0 wt % to 15 wt %. Preferably the
curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0231] In one embodiment, the curable secondary composition
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
tris(2-hydroxyethyl) isocyanurate triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0232] In one embodiment, the curable secondary composition
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris(2-hydroxyethyl) isocyanurate triacrylate monomer in an
amount in the range from 2.0 wt % to 25 wt %, or in the range from
5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0233] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an alkoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0234] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an ethoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0235] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an alkoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0236] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
an ethoxylated trimethylolpropane triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0237] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris[(acryloyloxy)alkyl] isocyanurate monomer in an amount in the
range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20
wt %, or in the range from 8.0 wt % to 15 wt %. Preferably the
curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0238] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris[(acryloyloxy)alkyl] isocyanurate monomer in an amount in the
range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt % to 20
wt %, or in the range from 8.0 wt % to 15 wt %. Preferably the
curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0239] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an alkoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
tris(2-hydroxyethyl) isocyanurate triacrylate monomer in an amount
in the range from 2.0 wt % to 25 wt %, or in the range from 5.0 wt
% to 20 wt %, or in the range from 8.0 wt % to 15 wt %. Preferably
the curable secondary coating composition lacks an alkoxylated
bisphenol-A diacrylate having a degree of alkoxylation greater than
17, or greater than 20, or greater than 25, or in the range from 15
to 40, or in the range from 20 to 35.
[0240] In one embodiment, the curable secondary composition
includes bisphenol-A epoxy diacrylate monomer in an amount greater
than 5.0 wt %, or greater than 10 wt %, or greater than 15 wt %, or
in the range from 5.0 wt % to 20 wt % or in the range from 8 wt %
to 17 wt %, or in the range from 10 wt % to 15 wt %, and further
includes an ethoxylated bisphenol-A diacrylate monomer in an amount
greater than 55 wt %, or greater than 60 wt %, or greater than 65
wt %, or greater than 70 wt %, or in the range from 55 wt % to 80
wt %, or in the range from 60 wt % to 75 wt %, and further includes
a tris(2-hydroxyethyl) isocyanurate triacrylate monomer in an
amount in the range from 2.0 wt % to 25 wt %, or in the range from
5.0 wt % to 20 wt %, or in the range from 8.0 wt % to 15 wt %.
Preferably the curable secondary coating composition lacks an
alkoxylated bisphenol-A diacrylate having a degree of alkoxylation
greater than 17, or greater than 20, or greater than 25, or in the
range from 15 to 40, or in the range from 20 to 35.
[0241] The optional oligomer present in the radiation-curable
secondary coating composition is preferably a compound with
urethane linkages. In one aspect, the optional oligomer is a
reaction product of a polyol compound, a diisocyanate compound, and
a hydroxy-functional acrylate compound. Reaction of the polyol
compound with the diisocyanate compound provides a urethane linkage
and the hydroxy-functional acrylate compound reacts with isocyanate
groups to provide terminal acrylate groups. If present, the total
oligomer content in the radiation-curable secondary coating
composition is less than 3.0 wt %, or less than 2.0 wt %, or less
than 1.0 wt %, or in the range from 0 wt % to 3.0 wt %, or in the
range from 0.1 wt % to 3.0 wt %, or in the range from 0.2 wt % to
2.0 wt %, or in the range from 0.3 wt % to 1.0 wt %. In one
embodiment, the radiation-curable secondary coating composition is
devoid of oligomers.
[0242] One class of optional oligomers is ethylenically unsaturated
oligomers. When included, suitable oligomers may be monofunctional
oligomers, multifunctional oligomers, or a combination of a
monofunctional oligomer and a multifunctional oligomer. If present,
the oligomer component may include aliphatic and aromatic urethane
(meth)acrylate oligomers, urea (meth)acrylate oligomers, polyester
and polyether (meth)acrylate oligomers, acrylated acrylic
oligomers, polybutadiene (meth)acrylate oligomers, polycarbonate
(meth)acrylate oligomers, and melamine (meth)acrylate oligomers or
combinations thereof. The curable secondary coating composition may
be free of urethane groups, urethane acrylate compounds, urethane
oligomers, or urethane acrylate oligomers.
[0243] Urethane oligomers may be prepared by reacting an aliphatic
or aromatic diisocyanate with a dihydric polyether or polyester,
most typically a polyoxyalkylene glycol such as a polyethylene
glycol. Moisture-resistant oligomers may be synthesized in an
analogous manner, except that polar polyethers or polyester glycols
are avoided in favor of predominantly saturated and predominantly
nonpolar aliphatic diols. These diols may include alkane or
alkylene diols of from about 2-250 carbon atoms that may be
substantially free of ether or ester groups.
[0244] Polyurea elements may be incorporated in oligomers prepared
by these methods, for example, by substituting diamines or
polyamines for diols or polyols in the course of synthesis.
[0245] The curable secondary coating composition also includes a
photoinitiator and optionally includes additives such as
anti-oxidant(s), optical brightener(s), amine synergist(s),
tackifier(s), catalyst(s), a carrier or surfactant, and a
stabilizer as described above in connection with the curable
primary coating composition.
[0246] The curable secondary coating composition includes a single
photoinitiator or a combination of two or more photoinitiators. The
total photoinitiator content of the curable secondary coating
composition is up to about 10 wt %, or between about 0.5 wt % and
about 6 wt %.
[0247] A representative antioxidant is thiodiethylene
bis[3-(3,5-di-tert-butyl)-4-hydroxy-phenyl) propionate] (e.g.,
IRGANOX 1035, available from BASF). In some aspects, an antioxidant
is present in the curable secondary coating composition in an
amount greater than 0.25 wt %, or greater than 0.50 wt %, or
greater than 0.75 wt %, or greater than 1.0 wt %, or an amount in
the range from 0.25 wt % to 3.0 wt %, or an amount in the range
from 0.50 wt % to 2.0 wt %, or an amount in the range from 0.75 wt
% to 1.5 wt %.
[0248] Representative optical brighteners include TINOPAL OB
(available from BASF); Blankophor KLA (available from Bayer);
bisbenzoxazole compounds; phenylcoumarin compounds; and
bis(styryl)biphenyl compounds. In an embodiment, the optical
brightener is present in the curable secondary coating composition
at a concentration of 0.005 wt % to 0.3 wt %.
[0249] Representative amine synergists include triethanolamine;
1,4-diazabicyclo[2.2.2]octane (DABCO), triethylamine, and
methyldiethanolamine. In an embodiment, an amine synergist is
present at a concentration of 0.02 wt % to 0.5 wt %.
[0250] Secondary Coating-Properties. Relevant properties of the
secondary coating include radius, thickness, Young's modulus,
tensile strength, yield strength, elongation at yield, glass
transition temperature, and puncture resistance
[0251] The radius r.sub.6 of the secondary coating is less than or
equal to 95.0 microns, or less than or equal to 90.0 microns, or
less than or equal to 85.0 microns, or less than or equal to 80.0
microns.
[0252] To facilitate decreases in the diameter of the optical
fiber, it is preferable to minimize the thickness r.sub.6-r.sub.5
of the secondary coating. The thickness r.sub.6-r.sub.5 of the
secondary coating is less than or equal to 25.0 microns, or less
than or equal to 20.0 microns, or less than or equal to 15.0
microns, or less than or equal to 10.0 microns, or in the range
from 5.0 microns to 25.0 microns, or in the range from 8.0 microns
to 20.0 microns, or in the range from 10.0 microns to 18.0 microns,
or in the range from 12.0 microns to 16.0 microns.
[0253] To facilitate puncture resistance and high protective
function, it is preferable for the secondary coating to have a high
Young's modulus. The Young's modulus of the secondary coating is
greater than or equal to 1600 MPa, or greater than or equal to 1800
MPa, or greater than or equal to 2000 MPa, or greater than or equal
to 2200 MPa, or in the range from 1600 MPa to 2800 MPa, or in the
range from 1800 MPa to 2600 MPa.
[0254] Design Examples--Optical Fibers
[0255] Seven modeled design examples Ex. 1 through Ex. 7 of the
optical fiber 100 with different core/cladding designs and optical
attributes are set forth in Tables 1-2 below. Ex. 1 and Ex. 2 are
step index fibers having a relative refractive index profile of the
type shown in FIG. 6A. Ex. 1 and Ex. 2 comprise a Cl-doped silica
core surrounded by a single cladding consisting of undoped silica.
Ex. 3 is a step index fiber having a relative refractive index
profile of the type shown in FIG. 6D. Ex. 3 comprises a Cl-doped
silica core surrounded by a downdoped silica inner cladding
(corresponding to a trench), which is surrounded by an undoped
silica outer cladding. Ex. 4 is a step index fiber having a
relative refractive index profile of the type shown in FIG. 6C. Ex.
4 comprises a Cl-doped silica core surrounded by an undoped silica
inner cladding, which is surrounded by an updoped silica outer
cladding. Ex. 5 is a fiber having a relative refractive index
profile shown in FIG. 6C having a high alpha core, a depressed
inner cladding and an outer cladding. Ex. 5 comprises a Cl-doped
silica core surrounded by a downdoped inner cladding (corresponding
to a trench), which is surrounded by an undoped silica outer
cladding. Ex. 6 is a having a relative refractive index profile
shown in FIG. 6C having a high alpha core, a depressed inner
cladding and an outer cladding. Ex. 6 comprise a Cl-doped silica
core surrounded by a downdoped inner cladding (corresponding to a
trench), which is surrounded by an updoped silica outer cladding.
Ex. 7 is a fiber having a relative refractive index profile shown
in FIG. 6C having a high alpha core, a depressed inner cladding and
an outer cladding. Ex. 7 comprises a Cl-doped silica core
surrounded by an undoped inner cladding (corresponding to a
trench), which is surrounded by an updoped silica outer cladding.
The radius r.sub.4 of the outer cladding of each of Ex. 1-Ex. 7 is
62.5 microns.
TABLE-US-00001 TABLE 1 Parameter Ex. 1 Ex. 2 Ex. 3 Ex. 4
.DELTA..sub.1 (%) 0.34 0.34 0.34 0.347 Core dopant Cl Cl Cl Cl Core
alpha 100 100 100 100 Cl in core (wt. %) 5.40 5.40 5.40 5.51
r.sub.1 (microns) 4.2 4.45 4.9 5.1 .DELTA..sub.2 (%) 0 0 -0.07 0
Inner cladding dopant none none F none F in first clad (wt %) 0 0
0.23 0 F in first clad (mole %) 0 0 0.7 0 r.sub.2 14.8 15.4
.DELTA..sub.4 (%) 0 0 0 0.07 Outer Cladding Dopant none none none
Cl 22-meter cable cutoff 1210 1250 1209 1209 .lamda..sub.CC (nm)
Zero-dispersion wave- 1306 1301 1289 1278 length (nm) Mode field
diameter at 9.1 9.2 9.1 9.3 1310 nm (microns) Effective area at
1310 66.2 68 68.6 72 nm (micron.sup.2) Dispersion at 1310 nm 0.35
0.75 2.55 2.87 (ps/nm/km) Dispersion Slope at 0.086 0.0866 0.0881
0.0888 1310 nm (ps/nm.sup.2/km) Mode field diameter at 10.3 10.4 10
10.2 1550 nm (microns) Effective area at 1550 80.2 83.6 80.1 83.3
nm (micron.sup.2) Dispersion at 1550 nm 17 17.5 19.6 20.1
(ps/nm/km) Dispersion Slope at 0.0576 0.0579 0.0587 0.0593 1550 nm
(ps/nm.sup.2/km) Attenuation at 1550 <0.170 <0.170 <0.170
<0.170 nm (dB/km)
[0256] All the exemplary optical fibers in Ex. 1-Ex. 4 set forth in
Table 1 have a Cl-doped core design with a chlorine concentration
greater than 3 wt % and an attenuation of less than 0.170 dB/km at
1550 nm.
TABLE-US-00002 TABLE 2 Parameter Ex. 5 Ex. 6 Ex. 7 A.sub.1 (%) 0.2
0.2 0.25 Core alpha 20 20 20 Cl conc in core (wt %) 3.17 3.17 3.17
r.sub.1 (microns) 6.2 7.3 7.4 .DELTA..sub.2 (%) -0.12 -0.05 0
r.sub.2 (microns) 22 25 25 V.sub.2 (% .DELTA.micron.sup.2) 107 57
62 .DELTA..sub.4 (%) 0 0.02 0.055 r.sub.4 (microns) 62.5 62.5 62.5
Mode field diameter 11.79 13.571 13.65 at 1550 nm (microns)
Effective area at 112.3 150.1 152.3 1550 nm (micron.sup.2)
Dispersion at 1550 20.947 21.3 21.27 nm (ps/nm/km) Dispersion Slope
at 0.0609 0.061 0.061 1550 nm (ps/nm.sup.2/km) 22-meter cable
cutoff <1400 <1430 <1450 .lamda..sub.CC (nm) 20 mm bend
loss at 0.9332 2.0855 2.0497 1550 nm (dB/turn) 30 mm bend loss at
0.2382 0.5117 0.3109 1550 nm (dB/turn) 40 mm bend loss at 0.0968
0.1287 0.0603 1550 nm (dB/turn) 50 mm bend loss at 0.0394 0.0324
0.0117 1550 nm (dB/turn) 60 mm bend loss at 0.0160 0.0081 0.0023
1550 nm (dB/turn) Attenuation at 1550 <0.170 <0.170 <0.170
nm (dB/km)
[0257] All the exemplary optical fibers in Ex. 5-Ex. 7 set forth in
Table 2 have a Cl-doped core design with a chlorine concentration
greater than 3 wt % and an attenuation of less than 0.170 dB/km at
1550 nm.
[0258] The following examples illustrate preparation of a
representative primary and secondary coatings. Measurements of
selected properties of the representative primary and secondary
coatings are also described. In addition, modeled properties of
glass fibers coated with primary and secondary coatings at
different coating thickness and modulus are presented.
[0259] Design Examples--Primary Coating
[0260] Primary Coating--Oligomer. The primary coating composition
included an oligomer. For purposes of illustration, preparation of
exemplary oligomers from H12MDI (4,4'-methylene bis(cyclohexyl
isocyanate), PPG4000 (polypropylene glycol with M.sub.n.about.4000
g/mol) and HEA (2-hydroxyethyl acrylate) in accordance with the
reaction scheme hereinabove is described. All reagents were used as
supplied by the manufacturer and were not subjected to further
purification. H12MDI was obtained from ALDRICH. PPG4000 was
obtained from COVESTRO and was certified to have an unsaturation of
0.004 meq/g as determined by the method described in the standard
ASTM D4671-16. HEA was obtained from KOWA.
[0261] The relative amounts of the reactants and reaction
conditions were varied to obtain a series of six oligomers.
Oligomers with different initial molar ratios of the constituents
were prepared with molar ratios of the reactants satisfying
H12MDI:HEA:PPG4000=n:m:p, where n was in the range from 3.0 to 4.0,
m was in the range from 1.5n to 3 to 2.5n to 5, and p=2. In the
reactions used to form the oligomers materials, dibutyltin
dilaurate was used as a catalyst (at a level of 160 ppm based on
the mass of the initial reaction mixture) and
2,6-di-tert-butyl-4-methylphenol (BHT) was used as an inhibitor (at
a level of 400 ppm based on the mass of the initial reaction
mixture).
[0262] The amounts of the reactants used to prepare each of the six
oligomers are summarized in Table 3 below. The six oligomers are
identified by separate Sample numbers 1-6. Corresponding sample
numbers will be used herein to refer to coating compositions and
cured films formed from coating compositions that individually
contain each of the six oligomers. The corresponding mole numbers
used in the preparation of each of the six samples are listed in
Table 4 below. The mole numbers are normalized to set the mole
number p of PPG4000 to 2.0.
TABLE-US-00003 TABLE 3 Reactants and Amounts for Exemplary Oligomer
Samples 1-6 Sample H12MDI (g) HEA (g) PPG4000 (g) 1 22 6.5 221.5 2
26.1 10.6 213.3 3 26.1 10.6 213.3 4 27.8 12.3 209.9 5 27.8 12.3
209.9 6 22 6.5 221.5
TABLE-US-00004 TABLE 4 Mole Numbers for Oligomer Samples 1-6 H12MDI
HEA PPG4000 Mole Number Mole Number Mole Number Di-adduct Sample
(n) (m) (p) (wt %) 1 3.0 2.0 2.0 1.3 2 3.7 3.4 2.0 3.7 3 3.7 3.4
2.0 3.7 4 4.0 4.0 2.0 5.0 5 4.0 4.0 2.0 5.0 6 3.0 2.0 2.0 1.3
[0263] The oligomers were prepared by mixing 4,4'-methylene
bis(cyclohexyl isocyanate), dibutyltin dilaurate and
2,6-di-tert-butyl-4 methylphenol at room temperature in a 500 mL
flask. The 500 mL flask was equipped with a thermometer, a
CaCl.sub.2) drying tube, and a stirrer. While continuously stirring
the contents of the flask, PPG4000 was added over a time period of
30-40 minutes using an addition funnel. The internal temperature of
the reaction mixture was monitored as the PPG4000 was added and the
introduction of PPG4000 was controlled to prevent excess heating
(arising from the exothermic nature of the reaction). After the
PPG4000 was added, the reaction mixture was heated in an oil bath
at about 70.degree. C. to 75.degree. C. for about 1 to 11/2 hours.
At various intervals, samples of the reaction mixture were
retrieved for analysis by infrared spectroscopy (FTIR) to monitor
the progress of the reaction by determining the concentration of
unreacted isocyanate groups. The concentration of unreacted
isocyanate groups was assessed based on the intensity of a
characteristic isocyanate stretching mode near 2265 cm.sup.-1. The
flask was removed from the oil bath and its contents were allowed
to cool to below 65.degree. C. Addition of supplemental HEA was
conducted to insure complete quenching of isocyanate groups. The
supplemental HEA was added dropwise over 2-5 minutes using an
addition funnel. After addition of the supplemental HEA, the flask
was returned to the oil bath and its contents were again heated to
about 70.degree. C. to 75.degree. C. for about 1 to 11/2 hours.
FTIR analysis was conducted on the reaction mixture to assess the
presence of isocyanate groups and the process was repeated until
enough supplemental HEA was added to fully react any unreacted
isocyanate groups. The reaction was deemed complete when no
appreciable isocyanate stretching intensity was detected in the
FTIR measurement. The HEA amounts listed in Table 1 include the
initial amount of HEA in the composition and any amount of
supplemental HEA needed to quench unreacted isocyanate groups.
[0264] The concentration (wt %) of di-adduct compound in each
oligomer was determined by gel permeation chromatography (GPC). A
Waters Alliance 2690 GPC instrument was used to determine the
di-adduct concentration. The mobile phase was THF. The instrument
included a series of three Polymer Labs columns. Each column had a
length of 300 mm and an inside diameter of 7.5 mm. Two of the
columns (columns 1 and 2) were sold under Part No. PL1110-6504 by
Agilent Technologies and were packed with PLgel Mixed D stationary
phase (polystyrene divinyl benzene copolymer, average particle
size=5 microns, specified molecular weight range=200 g/mol to
400,000 g/mol). The third column (column 3) was sold under Part No.
PL1110-6520 by Agilent Technologies and was packed with PLgel 100A
stationary phase (polystyrene divinyl benzene copolymer, average
particle size=5 microns, specified molecular weight range=up to
4,000 g/mol). The columns were calibrated with polystyrene
standards ranging from 162 g/mol to 6,980,000 g/mol using EasiCal
PS-1 & 2 polymer calibrant kits (Agilent Technologies Part Nos.
PL2010-505 and PL2010-0601). The GPC instrument was operated under
the following conditions: flow rate=1.0 mL/min, column
temperature=40.degree. C., injection volume=100 .mu.L, and run
time=35 min (isocratic conditions). The detector was a Waters
Alliance 2410 differential refractometer operated at 40.degree. C.
and sensitivity level 4. The samples were injected twice along with
a THF+0.05% toluene blank.
[0265] The amount (wt %) of di-adduct in the oligomers was
quantified using the preceding GPC system and technique. A
calibration curve was obtained using standard solutions containing
known amounts of the di-adduct compound (HEA-H12MDI-HEA) in THF.
Standard solutions with di-adduct concentrations of 115.2 .mu.g/g,
462.6 .mu.g/g, 825.1 .mu.g/g, and 4180 .mu.g/g were prepared. (As
used herein, the dimension ".mu.g/g" refers to .mu.g of di-adduct
per gram of total solution (di-adduct+THF)). Two 100 .mu.L aliquots
of each di-adduct standard solution were injected into the column
to obtain the calibration curve. The retention time of the
di-adduct was approximately 23 min and the area of the GPC peak of
the di-adduct was measured and correlated with di-adduct
concentration. A linear correlation of peak area as a function of
di-adduct concentration was obtained (correlation coefficient
(R.sup.2)=0.999564).
[0266] The di-adduct concentration in the oligomers was determined
using the calibration. Samples were prepared by diluting
.about.0.10 g of oligomeric material in THF to obtain a .about.1.5
g test solution. The test solution was run through the GPC
instrument and the area of the peak associated with the di-adduct
compound was determined. The di-adduct concentration in units of
.mu.g/g was obtained from the peak area and the calibration curve,
and was converted to wt % by multiplying by the weight (g) of the
test solution and dividing by the weight of the sample of
oligomeric material before dilution with THF. The wt % of di-adduct
compound present in each of the six oligomers prepared in this
example are reported in Table 4.
[0267] Through variation in the relative mole ratios of H12MDI,
HEA, and PPG4000, the illustrative oligomers include a polyether
urethane compound of the type shown in molecular formula (IV)
hereinabove and an enhanced concentration of di-adduct compound of
the type shown in molecular formula (V) hereinabove.
[0268] Primary Coating--Compositions. Oligomers corresponding to
Samples 1-6 were separately combined with other components to form
a series of six coating compositions. The amount of each component
in the coating composition is listed in Table 5 below. The entry in
Table 5 for the oligomer includes the combined amount of polyether
urethane acrylate compound and di-adduct compound present in the
oligomer. A separate coating composition was made for each of the
six exemplary oligomers corresponding to Samples 1-6, where the
amount of di-adduct compound in the oligomeric material
corresponded to the amount listed in Table 4.
TABLE-US-00005 TABLE 5 Coating Composition Component Amount
Oligomeric Material 49.10 wt % Sartomer SR504 45.66 wt % V-CAP/RC
1.96 wt % TPO 1.47 wt % Irganox 1035 0.98 wt % adhesion promoter
0.79 wt % Tetrathiol 0.03 wt %
[0269] Sartomer SR504 is ethoxylated(4)nonylphenol acrylate
(available from Sartomer). V-CAP/RC is N-vinylcaprolactam
(available from ISP Technologies). TPO is
2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (available from
BASF under the trade name Lucirin and functions as a
photoinitiator). Irganox 1035 is thiodiethylene
bis[3-(3,5-di-tert-butyl)-4-hydroxy-phenyl) propionate] (available
from BASF) and functions as an antioxidant. The adhesion promoters
were 3-acryloxypropyl trimethoxysilane (available from Gelest) and
3-mercaptopropyl trimethoxysilane (available from Aldrich).
3-acryloxypropyl trimethoxysilane was used for Samples 1, 3, and 5.
3-mercaptopropyl trimethoxysilane was used for Samples 2, 4, and 6.
Tetrathiol is a catalyst quencher.
[0270] The coating compositions of Table 5 were each formulated
using a high-speed mixer in an appropriate container heated to
60.degree. C., with a heating band or heating mantle. In each case,
the components were weighed into the container using a balance and
allowed to mix until the solid components were thoroughly dissolved
and the mixture appeared homogeneous. The oligomer and monomers
(SR504, NVC) of each composition were blended together for at least
10 minutes at 55.degree. C. to 60.degree. C. The photoinitiator,
antioxidant, and catalyst quencher were then added, and blending
was continued for one hour while maintaining a temperature of
55.degree. C. to 60.degree. C. Finally, the adhesion promoter was
added, and blending was continued for 30 minutes at 55.degree. C.
to 60.degree. C. to form the coating compositions.
[0271] Primary Coating--Properties--Tensile Properties. Tensile
properties (Young's modulus, tensile strength at yield, and
elongation at yield) were measured on films formed by curing the
six coating compositions. Separate films were formed from each
coating composition. Wet films of the coating composition were cast
on silicone release paper with the aid of a draw-down box having a
gap thickness of about 0.005''. The wet films were cured with a UV
dose of 1.2 J/cm.sup.2 (measured over a wavelength range of 225 to
424 nm by a Light Bug model IL490 from International Light) by a
Fusion Systems UV curing apparatus with a 600 W/in D-bulb (50%
Power and approximately 12 ft/min belt speed) to yield cured
coatings in film form. Cured film thickness was between about
0.0030'' and 0.0035''.
[0272] The films were aged (23.degree. C., 50% relative humidity)
for at least 16 hours prior to testing. Film samples were cut to
dimensions of 12.5 cm.times.13 mm using a cutting template and a
scalpel. Young's modulus, tensile strength at yield, and elongation
at yield were measured at room temperature (approximately
20.degree. C.) on the film samples using a MTS Sintech tensile test
instrument following procedures set forth in ASTM Standard D882-97.
Young's modulus is defined as the steepest slope of the beginning
of the stress-strain curve. Films were tested at an elongation rate
of 2.5 cm/min with the initial gauge length of 5.1 cm. The results
are shown in Table 6.
TABLE-US-00006 TABLE 6 Young's Modulus, Tensile Strength, and
Elongation of Film Samples Young's Modulus Tensile Strength
Elongation Sample (MPa) (MPa) (%) 1 0.72 0.51 137.9 2 0.57 0.44 173
3 1.0 0.86 132.8 4 0.71 0.45 122.3 5 0.72 0.56 157.4 6 0.33 0.33
311.9
[0273] Primary Coating Properties In Situ Modulus. In situ modulus
measurements of primary coating composition Samples 2, 3, and 5
were completed. In situ modulus measurements require forming the
primary coatings on a glass fiber having a diameter of 125 microns.
Each of Samples 2, 3, and 5 was separately applied as a primary
coating composition to a glass fiber as the glass fiber was being
drawn. The fiber draw speed was 50 m/s. The primary coating
compositions were cured using a stack of five LED sources. Each LED
source was operated at 395 nm and had an intensity of 12
W/cm.sup.2. Subsequent to application and curing of the primary
coating compositions, a secondary coating composition was applied
to each of the cured primary coatings and cured using UV sources to
form a secondary coating layer. The thickness of the primary
coating was 32.5 microns and the thickness of the secondary coating
was 26.0 microns.
[0274] The in situ modulus was measured using the following
procedure. A six-inch sample of fiber was obtained and a one-inch
section from the center of the fiber was window stripped and wiped
with isopropyl alcohol. The window-stripped fiber was mounted on a
sample holder/alignment stage equipped with 10 mm.times.5 mm
rectangular aluminum tabs that were used to affix the fiber. Two
tabs were oriented horizontally and positioned so that the short 5
mm sides were facing each other and separated by a 5 mm gap. The
window-stripped fiber was laid horizontally on the sample holder
across the tabs and over the gap separating the tabs. The coated
end of one side of the window-stripped region of the fiber was
positioned on one tab and extended halfway into the 5 mm gap
between the tabs. The one-inch window-stripped region extended over
the remaining half of the gap and across the opposing tab. After
alignment, the sample was moved and a small dot of glue was applied
to the half of each tab closest to the 5 mm gap. The fiber was then
returned to position and the alignment stage was raised until the
glue just touched the fiber. The coated end was then pulled away
from the gap and through the glue such that the majority of the 5
mm gap between the tabs was occupied by the window-stripped region
of the fiber. The portion of the window-stripped region remaining
on the opposing tab was in contact with the glue. The very tip of
the coated end was left to extend beyond the tab and into the gap
between the tabs. This portion of the coated end was not embedded
in the glue and was the object of the in situ modulus measurement.
The glue was allowed to dry with the fiber sample in this
configuration to affix the fiber to the tabs. After drying, the
length of fiber fixed to each of the tabs was trimmed to 5 mm. The
coated length embedded in glue, the non-embedded coated length (the
portion extending into the gap between the tabs), and the primary
diameter were measured.
[0275] The in situ modulus measurements were performed on a
Rheometrics DMTA IV dynamic mechanical testing apparatus at a
constant strain of 9e-6 l/s for a time of forty-five minutes at
room temperature (21.degree. C.). The gauge length was 15 mm. Force
and the change in length were recorded and used to calculate the in
situ modulus of the primary coating. The tab-mounted fiber samples
were prepared by removing any epoxy from the tabs that would
interfere with the 15 mm clamping length of the testing apparatus
to ensure that there was no contact of the clamps with the fiber
and that the sample was secured squarely to the clamps. The
instrument force was zeroed out. The tab to which the non-coated
end of the fiber was affixed was then mounted to the lower clamp
(measurement probe) of the testing apparatus and the tab to which
the coated end of the fiber was affixed was mounted to the upper
(fixed) clamp of the testing apparatus. The test was then executed
and the sample was removed once the analysis was completed.
[0276] The in situ modulus of primary coating Samples 2, 3, and 5
are listed in Table 7.
TABLE-US-00007 TABLE 7 In Situ Modulus of Selected Primary Coatings
Sample In-Situ Modulus (MPa) 2 0.27 3 0.33 5 0.3
[0277] Design Examples--Secondary Coating
[0278] Secondary Coating Compositions. Representative curable
secondary coating compositions are listed in Table 8.
TABLE-US-00008 TABLE 8 Secondary Coating Compositions Composition
Component KA KB KC KD SR601 (wt %) 72.0 30.0 30.0 30.0 SR602 (wt %)
37.0 37.0 37.0 SR349 (wt %) 30.0 15.0 SR399 (wt %) 15.0 SR499 (wt
%) 30.0 CD9038 (wt %) 10.0 Photomer 3016 (wt %) 15.0 TPO (wt %) 1.5
Irgacure 184 (wt %) 1.5 Irgacure 1850 (wt %) 3.0 3.0 3.0 Irganox
1035 (pph) 0.5 DC-190 (pph) 1.0
[0279] SR601 is ethoxylated (4) bisphenol A diacrylate (a monomer).
SR602 is ethoxylated (10) bisphenol A diacrylate (a monomer). SR349
is ethoxylated (2) bisphenol A diacrylate (a monomer). SR399 is
dipentaerythritol pentaacrylate. SR499 is ethoxylated (6)
trimethylolpropane triacrylate. CD9038 is ethoxylated (30)
bisphenol A diacrylate (a monomer). Photomer 3016 is bisphenol A
epoxy diacrylate (a monomer). TPO is a photoinitiator. Irgacure 184
is 1-hydroxycyclohexylphenyl ketone (a photoinitiator). Irgacure
1850 is bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine
oxide (a photoinitiator). Irganox 1035 is thiodiethylene
bis(3,5-di-tert-butyl)-4-hydroxyhydrocinnamate (an antioxidant).
DC190 is silicone-ethylene oxide/propylene oxide copolymer (a slip
agent). The concentration unit "pph" refers to an amount relative
to a base composition that includes all monomers, oligomers, and
photoinitiators. For example, for secondary coating composition KA,
a concentration of 1.0 pph for DC-190 corresponds to 1 g DC-190 per
100 g combined of SR601, CD9038, Photomer 3016, TPO, and Irgacure
184.
[0280] A comparative curable secondary coating composition (A) and
three representative curable secondary coating compositions (SB,
SC, and SD) within the scope of the disclosure are listed in Table
9.
TABLE-US-00009 TABLE 9 Secondary Coating Compositions Composition
Component A SB SC SD PE210 (wt %) 15.0 15.0 15.0 15.0 M240 (wt %)
72.0 72.0 72.0 62.0 M2300 (wt %) 10.0 -- -- -- M3130 (wt %) -- 10.0
-- -- M370 (wt %) -- -- 10.0 10.0 TPO (wt %) 1.5 1.5 1.5 1.5
Irgacure 184 (wt %) 1.5 1.5 1.5 1.5 Irganox 1035 (pph) 0.5 0.5 0.5
0.5 DC-190 (pph) 1.0 1.0 1.0 1.0
PE210 is bisphenol-A epoxy diacrylate (available from Miwon
Specialty Chemical, Korea), M240 is ethoxylated (4) bisphenol-A
diacrylate (available from Miwon Specialty Chemical, Korea), M2300
is ethoxylated (30) bisphenol-A diacrylate (available from Miwon
Specialty Chemical, Korea), M3130 is ethoxylated (3)
trimethylolpropane triacrylate (available from Miwon Specialty
Chemical, Korea), TPO (a photoinitiator) is
(2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (available from
BASF), Irgacure 184 (a photoinitiator) is
1-hydroxycyclohexyl-phenyl ketone (available from BASF), Irganox
1035 (an antioxidant) is benzenepropanoic acid,
3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester
(available from BASF). DC190 (a slip agent) is silicone-ethylene
oxide/propylene oxide copolymer (available from Dow Chemical). The
concentration unit "pph" refers to an amount relative to a base
composition that includes all monomers and photoinitiators. For
example, for secondary coating composition A, a concentration of
1.0 pph for DC-190 corresponds to 1 g DC-190 per 100 g combined of
PE210, M240, M2300, TPO, and Irgacure 184.
[0281] Secondary Coating--Properties. The Young's modulus, tensile
strength at break, and elongation at break of secondary coatings
made from secondary compositions A, KA, KB, KC, KD, SB, SC and SD
were measured.
[0282] Secondary Coating --Properties --Measurement Techniques.
Properties of secondary coatings were determined using the
measurement techniques described below:
[0283] Tensile Properties. The curable secondary coating
compositions were cured and configured in the form of cured rod
samples for measurement of Young's modulus, tensile strength at
yield, yield strength, and elongation at yield. The cured rods were
prepared by injecting the curable secondary composition into
Teflon.RTM. tubing having an inner diameter of about 0.025''. The
rod samples were cured using a Fusion D bulb at a dose of about 2.4
J/cm.sup.2 (measured over a wavelength range of 225-424 nm by a
Light Bug model IL390 from International Light). After curing, the
Teflon.RTM. tubing was stripped away to provide a cured rod sample
of the secondary coating composition. The cured rods were allowed
to condition for 18-24 hours at 23.degree. C. and 50% relative
humidity before testing. Young's modulus, tensile strength at
break, yield strength, and elongation at yield were measured using
a Sintech MTS Tensile Tester on defect-free rod samples with a
gauge length of 51 mm, and a test speed of 250 mm/min. Tensile
properties were measured according to ASTM Standard D882-97. The
properties were determined as an average of at least five samples,
with defective samples being excluded from the average.
[0284] Glass Transition Temperature. In situ T.sub.g measurements
of primary and secondary coatings were performed on fiber tube-off
samples obtained from coated fibers. The coated fibers included a
glass fiber having a diameter of 125 microns, a primary coating
with thickness 32.5 microns surrounding and in direct contact with
the glass fiber, and a secondary coating with thickness 26.0
microns surrounding and in direct contact with the glass fiber. The
glass fiber and primary coating were the same for all samples
measured. The primary coating was formed from the reference primary
coating composition described below. Samples with a comparative
secondary coating and a secondary coating in accordance with the
present disclosure were measured.
[0285] The fiber tube-off samples were obtained using the following
procedure: a 0.0055'' Miller stripper was clamped down
approximately 1 inch from the end of the coated fiber. The one-inch
region of fiber was plunged into a stream of liquid nitrogen and
held in the liquid nitrogen for 3 seconds. The coated fiber was
then removed from the stream of liquid nitrogen and quickly
stripped to remove the coating. The stripped end of the fiber was
inspected for residual coating. If residual coating remained on the
glass fiber, the sample was discarded and a new sample was
prepared. The result of the stripping process was a clean glass
fiber and a hollow tube of stripped coating that included intact
primary and secondary coatings. The hollow tube is referred to as a
"tube-off sample". The glass, primary and secondary coating
diameter were measured from the end-face of the unstripped
fiber.
[0286] In-situ Tg of the tube-off samples was run using a
Rheometrics DMTA IV test instrument at a sample gauge length of 9
to 10 mm. The width, thickness, and length of the tube-off sample
were input to the operating program of the test instrument. The
tube-off sample was mounted and then cooled to approximately
to85.degree. C. Once stable, the temperature ramp was run using the
following parameters: [0287] Frequency: 1 Hz [0288] Strain: 0.3%
[0289] Heating Rate: 2.degree. C./min. [0290] Final Temperature:
150.degree. C. [0291] Initial Static Force=20.0 g [0292]
Static>Dynamic Force by=10.0%
[0293] The in-situ Tg of a coating is defined as the maximum value
of tan .delta. in a plot of tan .delta. as a function of
temperature, where tan .delta. is defined as:
tan .delta.=E''/E'
and E'' is the loss modulus, which is proportional to the loss of
energy as heat in a cycle of deformation and E' is the storage or
elastic modulus, which is proportional to the energy stored in a
cycle of deformation.
[0294] The tube-off samples exhibited distinct maxima in the tan
.delta. plot for the primary and secondary coatings. The maximum at
lower temperature (about -50.degree. C.) corresponded to the
in-situ Tg for the primary coating and the maximum at higher
temperature (above 50.degree. C.) corresponded to the in-situ Tg
for the secondary coating.
[0295] In Situ Modulus of Secondary Coating. For secondary
coatings, the in situ modulus was measured using fiber tube-off
samples prepared from the fiber samples. A 0.0055 inch Miller
stripper was clamped down approximately 1 inch from the end of the
fiber sample. This one-inch region of fiber sample was immersed
into a stream of liquid nitrogen and held for 3 seconds. The fiber
sample was then removed and quickly stripped. The stripped end of
the fiber sample was then inspected. If coating remained on the
glass portion of the fiber sample, the tube-off sample was deemed
defective and a new tube-off sample was prepared. A proper tube-off
sample is one that stripped clean from the glass and consisted of a
hollow tube with primary and secondary coating. The glass, primary
and secondary coating diameter were measured from the end-face of
the un-stripped fiber sample.
[0296] The fiber tube-off samples were run using a Rheometrics DMTA
IV instrument at a sample gauge length 11 mm to obtain the in situ
modulus of the secondary coating. The width, thickness, and length
were determined and provided as input to the operating software of
the instrument. The sample was mounted and run using a time sweep
program at ambient temperature (21.degree. C.) using the following
parameters: [0297] Frequency: 1 Rad/sec [0298] Strain: 0.3% [0299]
Total Time=120 sec. [0300] Time Per Measurement=1 sec [0301]
Initial Static Force=15.0 g [0302] Static>Dynamic Force by=10.0%
Once completed, the last five E' (storage modulus) data points were
averaged. Each sample was run three times (fresh sample for each
run) for a total of fifteen data points. The averaged value of the
three runs was reported.
[0303] Puncture Resistance of Secondary Coating. Puncture
resistance measurements were made on samples that included a glass
fiber, a primary coating, and a secondary coating. The glass fiber
had a diameter of 125 microns. The primary coating was formed from
the reference primary coating composition listed in Table 10 below.
Samples with various secondary coatings were prepared as described
below. The thicknesses of the primary coating and secondary coating
were adjusted to vary the cross-sectional area of the secondary
coating as described below. The ratio of the thickness of the
secondary coating to the thickness of the primary coating was
maintained at about 0.8 for all samples.
[0304] The puncture resistance was measured using the technique
described in the article entitled "Quantifying the Puncture
Resistance of Optical Fiber Coatings", by G. Scott Glaesemann and
Donald A. Clark, published in the Proceedings of the 52.sup.nd
International Wire & Cable Symposium, pp. 237-245 (2003). A
summary of the method is provided here. The method is an
indentation method. A 4-centimeter length of optical fiber was
placed on a 3 mm-thick glass slide. One end of the optical fiber
was attached to a device that permitted rotation of the optical
fiber in a controlled fashion. The optical fiber was examined in
transmission under 100.times. magnification and rotated until the
secondary coating thickness was equivalent on both sides of the
glass fiber in a direction parallel to the glass slide. In this
position, the thickness of the secondary coating was equal on both
sides of the optical fiber in a direction parallel to the glass
slide. The thickness of the secondary coating in the directions
normal to the glass slide and above or below the glass fiber
differed from the thickness of the secondary coating in the
direction parallel to the glass slide. One of the thicknesses in
the direction normal to the glass slide was greater and the other
of the thicknesses in the direction normal to the glass slide was
less than the thickness in the direction parallel to the glass
slide. This position of the optical fiber was fixed by taping the
optical fiber to the glass slide at both ends and is the position
of the optical fiber used for the indentation test.
[0305] Indentation was carried out using a universal testing
machine (Instron model 5500R or equivalent). An inverted microscope
was placed beneath the crosshead of the testing machine. The
objective of the microscope was positioned directly beneath a 75
diamond wedge indenter that was installed in the testing machine.
The glass slide with taped fiber was placed on the microscope stage
and positioned directly beneath the indenter such that the width of
the indenter wedge was orthogonal to the direction of the optical
fiber. With the optical fiber in place, the diamond wedge was
lowered until it contacted the surface of the secondary coating.
The diamond wedge was then driven into the secondary coating at a
rate of 0.1 mm/min and the load on the secondary coating was
measured. The load on the secondary coating increased as the
diamond wedge was driven deeper into the secondary coating until
puncture occurred, at which point a precipitous decrease in load
was observed. The indentation load at which puncture was observed
was recorded and is reported herein as grams of force. The
experiment was repeated with the optical fiber in the same
orientation to obtain ten measurement points, which were averaged
to determine a puncture resistance for the orientation. A second
set of ten measurement points was taken by rotating the orientation
of the optical fiber by 180.degree..
[0306] Microbending. In the wire mesh covered drum test, the
attenuation of light at wavelength of 1550 nm through a coated
fiber having a length of 750 m was determined at room temperature.
The microbend induced attenuation was determined by the difference
between a zero-tension deployment and a high-tension deployment on
the wire mesh drum. Separate measurements were made for two winding
configurations. In the first configuration, the fiber was wound in
a zero-tension configuration on an aluminum drum having a smooth
surface and a diameter of approximately 400 mm. The zero-tension
winding configuration provided a stress-free reference attenuation
for light passing through the fiber. After sufficient dwell time,
an initial attenuation measurement was performed. In the second
winding configuration, the fiber sample was wound to an aluminum
drum that was wrapped with fine wire mesh. For this deployment, the
barrel surface of the aluminum drum was covered with wire mesh and
the fiber was wrapped around the wire mesh. The mesh was wrapped
tightly around the barrel without stretching and was kept intact
without holes, dips, tearing, or damage. The wire mesh material
used in the measurements was made from corrosion-resistant type 304
stainless steel woven wire cloth and had the following
characteristics: mesh per linear inch: 165.times.165, wire
diameter: 0.0019'', width opening: 0.0041'', and open area %: 44.0.
A 750 m length of coated fiber was wound at 1 m/s on the wire mesh
covered drum at 0.050 cm take-up pitch while applying 80 (+/-1)
grams of tension. The ends of the fiber were taped to maintain
tension and there were no fiber crossovers. The points of contact
of the wound fiber with the mesh impart stress to the fiber and the
attenuation of light through the wound fiber is a measure of
stress-induced (microbending) losses of the fiber. The wire drum
measurement was performed after a dwell time of 1-hour. The
increase in fiber attenuation (in dB/km) in the measurement
performed in the second configuration (wire mesh covered drum)
relative to the first configuration (smooth drum) was determined
for each wavelength. The average of three trials was determined at
each wavelength and is reported as the wire mesh microbend
loss.
[0307] Reference Primary Coating. In measurements of in situ glass
transition temperature (T.sub.g), puncture resistance, and wire
mesh covered drum microbending attenuation, the measurement samples
included a primary coating between the glass fiber and a secondary
coating. The primary coating composition had the formulation given
in Table 10 and is typical of commercially available primary
coating compositions.
TABLE-US-00010 TABLE 10 Reference Primary Coating Composition
Component Amount Oligomeric Material 50.0 wt % SR504 46.5 wt % NVC
2.0 wt % TPO 1.5 wt % Irganox 1035 1.0 pph 3-Acryloxypropyl
trimethoxysilane 0.8 pph Pentaerythritol tetrakis(3- 0.032 pph
mercapto propionate)
where the oligomeric material was prepared as described above from
H12MDI, HEA, and PPG4000 using a molar ratio n:m:p=3.5:3.0:2.0,
SR504 is ethoxylated(4)nonylphenol acrylate (available from
Sartomer), NVC is N-vinylcaprolactam (available from Aldrich), TPO
(a photoinitiator) is (2,4,6-trimethylbenzoyl)-diphenyl phosphine
oxide (available from BASF), Irganox 1035 (an antioxidant) is
benzenepropanoic acid,
3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester
(available from BASF), 3-acryloxypropyl trimethoxysilane is an
adhesion promoter (available from Gelest), and pentaerythritol
tetrakis(3-mercaptopropionate) (also known as tetrathiol, available
from Aldrich) is a chain transfer agent. The concentration unit
"pph" refers to an amount relative to a base composition that
includes all monomers, oligomers, and photoinitiators. For example,
a concentration of 1.0 pph for Irganox 1035 corresponds to 1 g
Irganox 1035 per 100 g combined of oligomeric material, SR504, NVC,
and TPO.
[0308] Secondary Coatings Properties Tensile Properties. The
results of tensile property measurements prepared from the curable
secondary compositions are shown in Table 11.
TABLE-US-00011 TABLE 11 Tensile Properties of Secondary Coatings
Tensile Elongation Yield Young's Strength at yield Strength Modulus
Composition (MPa) (%) (MPa) (MPa) KA 54.3 39.0 1528 KB 63.1 24.1
1703 KC 45.7 28.4 1242 KD 61.8 32.5 1837 A 86.09 4.60 48.21 2049 SB
75.56 4.53 61.23 2532 SC 82.02 4.76 66.37 2653 SD 86.08 4.87 70.05
2776
[0309] The results show that secondary coatings prepared from
compositions SB, SC, and SD exhibited higher Young's modulus, and
higher yield strength than the secondary coating prepared from
comparative composition A. The higher values represent improvements
that make secondary coatings prepared for the curable coating
compositions disclosed herein better suited for small diameter
optical fibers. More specifically, the higher values enable use of
thinner secondary coatings on optical fibers without sacrificing
performance. Thinner secondary coatings reduce the overall diameter
of the optical fiber and provide higher fiber counts in cables of a
given cross-sectional area.
[0310] The Young's modulus of secondary coatings prepared as cured
products from the curable secondary coating compositions disclosed
herein is greater than 2400 MPa, or greater than 2500 MPa, or
greater than 2600 MPa, or greater than 2700 MPa, or in the range
from 2400 MPa to 3000 MPa, or in the range from 2600 MPa to 2800
MPa.
[0311] The yield strength of secondary coatings prepared as cured
products from the curable secondary coating compositions disclosed
herein is greater than 55 MPa, or greater than 60 MPa, or greater
than 65 MPa, or greater than 70 MPa, or in the range from 55 MPa to
75 MPa, or in the range from 60 MPa to 70 MPa.
[0312] Secondary Coatings Properties Puncture Resistance. The
puncture resistance of secondary coatings made from comparative
curable secondary coating composition A, a commercial curable
secondary coating composition (CPC6e) from a commercial vendor (DSM
Desotech) having a proprietary composition, and curable secondary
coating composition SD was determined according to the method
described above. Several fiber samples with each of the three
secondary coatings were prepared. Each fiber sample included a
glass fiber with a diameter of 125 microns, a primary coating
formed from the reference primary coating composition listed in
Table 10, and one of the three secondary coatings. Samples with
various secondary coatings were prepared. The thicknesses of the
primary coating and secondary coating were adjusted to vary the
cross-sectional area of the secondary coating as shown in FIG. 7.
The ratio of the thickness of the secondary coating to the
thickness of the primary coating was maintained at about 0.8 for
all samples.
[0313] Fiber samples with a range of thicknesses were prepared for
each of the secondary coatings to determine the dependence of
puncture load on the thickness of the secondary coating. One
strategy for achieving higher fiber count in cables is to reduce
the thickness of the secondary coating. As the thickness of the
secondary coating is decreased, however, its performance diminishes
and its protective function is compromised. Puncture resistance is
a measure of the protective function of a secondary coating. A
secondary coating with a high puncture resistance withstands
greater impact without failing and provides better protection for
the glass fiber.
[0314] The puncture load as a function of cross-sectional area for
the three coatings is shown in FIG. 7. Cross-sectional area is
selected as a parameter for reporting puncture load because an
approximately linear correlation of puncture load with
cross-sectional area of the secondary coating was observed. Traces
82, 84, and 86 shows the approximate linear dependence of puncture
load on cross-sectional area for the comparative secondary coatings
obtained by curing the comparative CPC6e secondary coating
composition, the comparative curable secondary coating composition
A, and curable secondary coating composition SD; respectively. The
vertical dashed lines are provided as guides to the eye at
cross-sectional areas of 10000 micron.sup.2, 15000 micron.sup.2,
and 20000 micron.sup.2 as indicated.
[0315] The CPC6e secondary coating depicted in Trace 82 corresponds
to a conventional secondary coating known in the art. The
comparative secondary coating A depicted in Trace 84 shows an
improvement in puncture load for high cross-sectional areas. The
improvement, however, diminishes as the cross-sectional area
decreases. This indicates that a secondary coating obtained as a
cured product from comparative curable secondary coating
composition A is unlikely to be suitable for low diameter, high
fiber count applications. Trace 86, in contrast, shows a
significant increase in puncture load for the secondary coating
obtained as a cured product from curable secondary coating
composition SD. At a cross-sectional area of 7000 micron.sup.2, for
example, the puncture load of the secondary coating obtained from
curable secondary coating composition SD is 50% or more greater
than the puncture load of either of the other two secondary
coatings.
[0316] The puncture load of secondary coatings formed as cured
products of the curable secondary coating compositions disclosed
herein at a cross-sectional area of 10000 micron.sup.2 is greater
than 36 g, or greater than 40 g, or greater than 44 g, or greater
than 48 g, or in the range from 36 g to 52 g, or in the range from
40 g to 48 g. The puncture load of secondary coatings formed as
cured products of the curable secondary coating compositions
disclosed herein at a cross-sectional area of 15000 micron.sup.2 is
greater than 56 g, or greater than 60 g, or greater than 64 g, or
greater than 68 g, or in the range from 56 g to 72 g, or in the
range from 60 g to 68 g. The puncture load of secondary coatings
formed as cured products of the curable secondary coating
compositions disclosed herein at a cross-sectional area of 20000
micron.sup.2 is greater than 68 g, or greater than 72 g, or greater
than 76 g, or greater than 80 g, or in the range from 68 g to 92 g,
or in the range from 72 g to 88 g. Embodiments include secondary
coatings having any combination of the foregoing puncture
loads.
[0317] As used herein, normalized puncture load refers to the ratio
of puncture load to cross-sectional area. The puncture load of
secondary coatings formed as cured products of the curable
secondary coating compositions disclosed herein have a normalized
puncture load greater than 3.2.times.10.sup.-3 g/micron.sup.2, or
greater than 3.6.times.10.sup.-3 g/micron.sup.2, or greater than
4.0.times.10.sup.-3 g/micron.sup.2, or greater than
4.4.times.10.sup.-3 g/micron.sup.2, or greater than
4.8.times.10.sup.-3 g/micron.sup.2, or in the range from
3.2.times.10.sup.-3 g/micron.sup.2 to 5.6.times.10.sup.-3
g/micron.sup.2, or in the range from 3.6.times.10.sup.-3
g/micron.sup.2 to 5.2.times.10.sup.-3 g/micron.sup.2, or in the
range from 4.0.times.10.sup.-3 g/micron.sup.2 to
4.8.times.10.sup.-3 g/micron.sup.2.
[0318] Secondary Coatings--Properties --Microbending. The
attenuation due to microbending of optical fibers was measured
according to the wire mesh covered drum test described above. The
optical fiber samples had a glass fiber with the relative
refractive index profile 90 shown in FIG. 6. The glass fiber had a
radius r.sub.4=62.5 microns and was surrounded by a primary coating
with thickness 36.5 microns, which was surrounded by a secondary
coating with thickness 26 microns. The primary coating was formed
from the reference primary coating composition listed in Table 10
and the secondary coating was formed from comparative coating
composition A listed in Table 9. Measurements were made on several
optical fibers and attenuation at 1550 nm as determined by the wire
mesh covered drum test was observed to be between 0.05 dB/km and
0.8 dB/km for all samples. The attenuation of the optical fibers is
less than 1.0 dB/km, or less than 0.8 dB/km, or less than 0.6
dB/km, or less than 0.4 dB/km, or less than 0.2 dB/km, or in the
range from 0.05 dB/km-1.0 dB/km, or in the range from 0.15 dB/km
-0.80 dB/km, or in the range from 0.30 dB/km-0.70 dB/km.
[0319] Design Examples--Coated Optical Fibers
[0320] Modeled Results. The experimental examples and principles
disclosed herein indicate that by varying the mole numbers n, m,
and p, it is possible to control the relative amount of di-adduct
compound in the oligomer as well as the properties of cured films
formed from the primary coating compositions over a wide range,
including the ranges specified herein for Young's modulus and in
situ modulus. Similarly, variations in the type and concentration
of different monomers in the secondary composition leads to
variations in the Young's modulus over the range disclosed herein.
Curing dose is another parameter that can be used to vary modulus
of primary and secondary coatings formed from the curable
compositions disclosed herein.
[0321] To examine the effect of the thickness and modulus of the
primary and secondary coatings on transmission of a radial force to
a glass fiber, a series of modeled examples was considered. In the
model, a radial external load P was applied to the surface of the
secondary coating of an optical fiber and the resulting load at the
surface of the glass fiber was calculated. The glass fiber was
modeled with a Young's modulus of 73.1 GPa (consistent with silica
glass) and a diameter of 125 microns. The Poisson ratios v.sub.p
and v.sub.s of the primary and secondary coatings were fixed at
0.48 and 0.33, respectively. A comparative sample C1 and six
samples M1-M6 in accordance with the present disclosure were
considered. The comparative sample included primary and secondary
coatings with thicknesses and moduli consistent with optical fibers
known in the art. Samples M1-M6 are examples with reduced
thicknesses of the primary and secondary coatings. Parameters
describing the configurations of the primary and secondary coatings
are summarized in Table 12.
TABLE-US-00012 TABLE 12 Coating Properties of Modeled Optical
Fibers Primary Coating Secondary Coating In Situ Young's Modulus
Diameter Thickness Modulus Diameter Thickness Sample (MPa)
(microns) (microns) (MPa) (microns) (microns) C1 0.20 190 32.5 1600
242 26.0 M1 0.14 167 21.0 1900 200 16.5 M2 0.12 161 18.0 1900 190
14.5 M3 0.10 155 15.0 2000 180 12.5 M4 0.09 150 12.5 2300 170 10.0
M5 0.12 145 15.0 2200 170 12.5 M6 0.11 138 14.0 2200 160 11.0
[0322] Table 13 summarizes the load P1 at the outer surface of the
glass fiber as a fraction of load P applied to the surface of the
secondary coating. The ratio P1/P is referred to herein as the load
transfer parameter and corresponds to the fraction of external load
P transmitted through the primary and secondary coatings to the
surface of the glass fiber. The load P is a radial load and the
load transfer parameter P1/P was calculated from a model based on
the equations below:
P 1 P = 4 ( 1 - v p ) ( 1 - v s ) { A + B } ##EQU00006## where
##EQU00006.2## A = ( E s ( 1 + v p ) ( 1 - 2 v p ) ( 1 - ( r 4 / r
5 ) 2 ) ( 1 - ( r 5 / r 6 ) 2 ) E p ( 1 + v s ) ) ##EQU00006.3##
and ##EQU00006.4## B = ( ( 1 - 2 v p ( r 4 / r 5 ) 2 + ( r 4 / r 5
) 2 ) ( 1 - 2 v s ( r 5 / r 6 ) 2 + ( r 5 / r 6 ) 2 ) )
##EQU00006.5##
[0323] In the equations, v.sub.p and v.sub.s are the Poisson's
ratios of the primary and secondary coatings, r.sub.4 is the outer
radius of the glass fiber, r.sub.5 is the outer radius of the
primary coating, r.sub.6 is the outer radius of the secondary
coating, E.sub.p is the in situ modulus of the primary coating, and
E.sub.s is the Young's modulus of the secondary coating. The scaled
load transfer parameter P1/P (scaled) in Table 13 corresponds to
the ratio P1/P for each sample relative to comparative sample
Cl.
TABLE-US-00013 TABLE 13 Load Transfer Parameter (P1/P) at Surface
of Glass Fiber Sample P1/P P1/P (scaled) C1 0.0178 1.00 M1 0.0171
0.97 M2 0.0175 0.98 M3 0.0172 0.97 M4 0.0170 0.95 M5 0.0167 0.94 M6
0.0166 0.94
[0324] The modeled examples show that despite smaller coating
thicknesses, optical fibers having primary and secondary coatings
as described herein exhibit a reduction in the force experienced by
a glass fiber relative to a comparative optical fiber having
conventional primary and secondary coatings with conventional
thicknesses. The resulting reduction in overall size of the optical
fibers described herein enables higher fiber count in cables of a
given size (or smaller cable diameters for a given fiber count)
without increasing the risk of damage to the glass fiber caused by
external forces.
[0325] The scaled load transfer parameter P.sub.1/P (scaled) of the
secondary coating is less than 0.99, or less than 0.97, or less
than 0.95. The load transfer parameter P.sub.1/P of the secondary
coating is less than 0.0200, or less than 0.0180, or less than
0.0178, or less than 0.0176, or less than 0.0174, or less than
0.0172, or less than 0.0170, or less than 0.0168, or in the range
from 0.0160-0.0180, or in the range from 0.0162-0.0179, or in the
range from 0.0164-0.0178, or in the range from 0.0166-0.0177, or in
the range from 0.0168-0.0176.
[0326] Fabricating the Optical Fibers
[0327] FIG. 8 is a schematic diagram of an example optical fiber
drawing system ("drawing system") 200 for drawing a glass preform
100P into the optical fiber 100, according to some embodiments. The
optical fiber 100 can be fabricated using the drawing system 100
and fiber drawing techniques known in the art.
[0328] The core and cladding layers of the glass preform can be
produced in a single-step process or multi-step process using
chemical vapor deposition (CVD) methods which are well known in the
art. A variety of CVD processes are known and are suitable for
producing the core and cladding layers used in the optical fibers
of the present invention. They include outside vapor deposition
process (OVD) process, vapor axial deposition (VAD) process,
modified CVD (MCVD), and plasma-enhanced CVD (PECVD).
[0329] As shown in FIG. 8, the exemplary drawing system 200 can
include a draw furnace ("furnace") 102 for heating the glass
preform 100P to the glass melt temperature. In an example, the
fiber draw process is carried out a glass melt temperature, which
in an example is in the range from 1800.degree. C. to 1900.degree.
C. A preform holder 116 is used to hold the glass preform 100P.
[0330] In some embodiments, the drawing system 200 also includes
non-contact measurement sensors 104A and 104B for measuring the
size of a drawn (bare) optical fiber 100 that exits the draw
furnace 102 for size (diameter) control. A cooling station 106 can
reside downstream of the measurement sensors 104A and 104B and is
configured to cool the bare optical fiber 100. A coating station
107 can reside downstream of the cooling station 106 and can be
configured to deposit one or more protective coating materials 71
onto the bare optical fiber 100 to form the protective coating 70
including the primary coating 72 and the secondary coating 74. A
tensioner 220 can reside downstream of the coating station 107. The
tensioner 220 can have a surface 222 that pulls (draws) the coated
optical fiber 100. A set of guide wheels 230 with respective
surfaces 232 resides downstream of the tensioner 220. The guide
wheels 230 can serve to guide the coated optical fiber 100 to a
fiber take-up spool ("spool") 250 for storage.
[0331] In some embodiments, the close-up inset I1 of FIG. 8 shows a
cross-sectional view of the glass preform 100P used to fabricate
the single-core optical fiber 100. The glass preform 100P includes
a preform core 10P and a preform cladding region 50P. In some
embodiments, the preform core 10P can be either a step refractive
index core or a graded refractive index core. The preform cladding
50P can include a preform inner cladding region, a preform
depressed index cladding region, and a preform outer cladding
region. The preform 100P can be fabricated using known techniques,
such as an outside vapor deposition (OVD) process. The close-up
inset 12 of FIG. 8 shows a cross-sectional view of the coated
optical fiber 100, which can be referred to the descriptions above
in connection with FIGS. 1 and 2.
[0332] The core and cladding of the disclosed optical fibers may be
produced in a single-step operation or multi-step operation by
methods which are well known in the art. Suitable methods include:
the flame combustion methods, flame oxidation methods, flame
hydrolysis methods, OVD (outside vapor deposition), IVD (inside
vapor deposition), VAD (vapor axial deposition), double crucible
method, rod-in-tube procedures, cane-in-soot method, and doped
deposited silica processes. A variety of CVD processes are known
and are suitable for producing the core, inner cladding region, and
outer cladding region used in the optical fibers of the present
disclosure. They include external CVD processes, axial vapor
deposition processes, modified CVD (MCVD), inside vapor deposition,
and plasma-enhanced CVD (PECVD).
[0333] Suitable precursors for silica include SiCl.sub.4 and
organosilicon compounds. Organosilicon compounds are silicon
compounds that include carbon. Organosilicon compounds may also
include oxygen and/or hydrogen. Examples of organosilicon compounds
include OMCTS (octamethylcyclotetrasiloxane), silicon alkoxides
(Si(OR).sub.4), organosilanes (SiR.sub.4), and
Si(OR).sub.xR.sub.4-x, where R is a carbon-containing organic group
or hydrogen and where R may be the same or different at each
occurrence, subject to the proviso that at least one R is a
carbon-containing organic group. Suitable precursors for chlorine
doping include Cl.sub.2, SiC.sub.4, Si.sub.2Cl.sub.6,
Si.sub.2OCl.sub.6, SiC.sub.3H, and CCl.sub.4. Suitable precursors
for fluorine doping include F.sub.2, CF.sub.4, and SiF.sub.4.
Summary and Clauses of the Description
[0334] Accordingly, one aspect of the present disclosure provides
optical fiber cables having high transmission capacity, low
transmission loss, similar size to traditional cables or cables
with higher fiber densities. Another aspect of the present
disclosure provides optical fibers in the cables having small
diameter, low transmission loss, low microbending loss, and high
puncture resistance.
[0335] While various embodiments have been described herein, they
have been presented by way of example only, and not limitation. It
should be apparent that adaptations and modifications are intended
to be within the meaning and range of equivalents of the disclosed
embodiments, based on the teaching and guidance presented herein.
It therefore will be apparent to one skilled in the art that
various changes in form and detail can be made to the embodiments
disclosed herein without departing from the spirit and scope of the
present disclosure. The elements of the embodiments presented
herein are not necessarily mutually exclusive, but may be
interchanged to meet various needs as would be appreciated by one
of skill in the art.
[0336] It is to be understood that the phraseology or terminology
used herein is for the purpose of description and not of
limitation. The breadth and scope of the present disclosure should
not be limited by any of the above-described exemplary embodiments,
but should be defined only in accordance with the following claims
and their equivalents.
* * * * *